Scar

His real name is never revealed, but he is referred to as "Scar" because of the X-shaped scar on his face. Scar's right arm, which is tattooed with a rare transmutation circle, was given to him by his brother shortly before he died.

Scar believes himself to be an instrument of God, and kills State Alchemists using his alchemical skills, despite the fact that he believes alchemy is an abomination against the natural world.

Manga
In the manga, he shares many attributes with the anime version, with a few exceptions. Differing from the anime, his country of heritage is called "Ishbal" as opposed to "Ishval." Also as a contrast, he was responsible for the murder of Winry Rockbell's parents, in the place of Roy Mustang. The incident occurred as a result of his brother (Supposedly) giving up his life and arm to save Scar's after he had been gravely wounded. Enraged by his brother's death at the hands of Amestrians, he goes on a blind rampage and kills the Rockbells, who were treating his injuries, and nearly everyone around him. He is portrayed as more relentless and ruthless in his vengeance, while the anime had him as a good man who was consumed by revenge for his people. He is also an Ishbalan Warrior Priest, skilled in martial arts, and is physically larger, and more built, than his anime counterpart.

Scar is both a threat to the military and the Homunculi. While he targets primarily State Alchemists in the State military, his relentless quest threatens to destroy all of the Homunculi's precious alchemist human sacrifices. As such, they have made many attempts to kill him, albeit unsuccessfully. Although he is not the prime antagonist in the manga, he establishes himself early on as one of the most often encountered dangers by the Elrics.

Scar attacked the Elric brothers in East City, managing to destroy Edward's automail arm, and shattering Alphonse' armor as well, and is nearly caught by the military, but he escapes into the sewers. Lust and Gluttony find him in the sewers and attack him. Unable to beat them, he blows up the sewer and is washed down the river. Hawkeye finds his bloodied coat and he is assumed dead, but in reality he is being treated at an Ishbalan refugee camp. Yoki, who happens to be present there after his humiliation at the mining town, hires bounty hunters to capture him. Scar easily defeats the bounty hunters and leaves with Yoki, who finds May Chang lying on the streets out cold. When the Elric brothers try to beat him while capturing a homunculus, he is shot by Hawkeye. Just before Ed and Al beat him to the ground for killing Winry's parents, and some of the other state alchemists, May defends him and uses alchemy to escape, and later to heal his wound. He agrees to help May find her pet panda out of pity because May's clan was also under threat of extinction as the Ishbalans were.

Scar and May end up stumbling upon the Elric Brothers and Lin/Greed in the Homunculi lair, where Ed revealed to him the fact that Envy sparked the Ishbal rebellion. Scar demands an explanation for the act, vowing to send the Homunculi to Ishbala before declaring they deserve even less. Unlike the Elrics, Scar and May are able to use their alchemy when in the lair, and Scar makes use of this to create a dust bomb to cover his handing over of May to Alphonse while he escapes on his own. As he escapes, he hears Dr. Marcoh's voice in Father's hideout. He finds the doctor, who asks Scar to kill him. Scar agrees to fulfill Marcoh's wish in return for the true story behind the Ishbal Massacre.

Only in chapter 60, the flashback of the Ishbalan extermination campaign finally reveals the secret to Scar's arm. His brother, who had been doing research on Rentanjutsu (alchemy from Xing) and Renkinjutsu (alchemy from Amestris) in order to help Ishbalans win against the Amestris army, showed Scar and other men the products of his work: two tattooed arms. He explained to Scar the three parts of alchemy (understanding, deconstruction, and reconstruction), and that the tattoos on the right arm cause deconstruction while the left arm causes reconstruction. The significance of this innovation was that Scar's brother could bypass the need for a transmutation circle. While fighting Kimblee in the midst of the extermination, Scar lost his right arm and his brother. With the last of his strength, his brother had attached his own arm, through means of alchemy, to Scar. Even if Scar wanted to finally break Ishbalan teaching and perform transmutation alchemy, he cannot because his right arm is only designed for destroying (or decomposing).

After learning the truth behind his brother's research, Scar decides to spare Marcoh's life to help him learn more. He uses his right arm to partially destroy Marcoh's face, disfiguring the doctor's skin and thus giving him a disguise. Scar and his group make their way to the North where the secrets of his brother's research are hidden. Scar encounters Kimblee on a train, where they fight, and Scar injures Kimblee and forces him to escape.

By Chapter 69, the four members of Scar's party (Scar, Yoki, May, Marcoh) hold up in a cabin in the snowy region of Briggs. Marcoh and May have recovered Scar's brother's journals, but the most important parts are written in undecipherable ancient Ishbalan writing. Marcoh hopes that Scar, as a warrior priest, can understand them to help their research. This theory is not tested as for the fact that immediately after Scar gets to the cabin with Yoki, he tells his party that they need to move to a new hiding spot.

Later, while Scar is looking for supplies, two central soldiers who he attacked before getting to the cabin, show up and retaliates, performing their capabilities as human chimeras. They are soon subdued by the Elric brothers, who pretend they don't recognize them as their supposed allies. Scar quickly attacks the brothers, but falters as he notices Winry, which allows the brothers to trap him and his arm. Major Miles and his soldiers arrive and order back-up, while Winry questions Scar as to why he killed her parents. Scar claims he has no legitimate reason and that Winry has every right to take her revenge.

Winry, however, chooses to endure and not exact revenge on Scar and even bandages him, stating that it would be something her parents would do. Nevertheless, she still does not forgive his actions. Major Miles then laments his condemning of a fellow Ishbalan and Scar has a flashback of his master, preaching that even though what the Amestrian military has done to them is unforgivable, as humans, they must endure it so as to sever the bond of hatred and keep their own dignity so they won't be the same as vengeful beasts, and that his brother's theory about the flow of energy in the world, will grow positive if people build positive feelings and become able to hold negative feelings.

However, when Scar is about to be taken, Marcoh appears, begging them not to take him yet. Marcoh asks Briggs' authorities to let Scar go, at least for a while. Miles asks Scar to swear upon his Ishbalan blood to give himself over after his part is done, which Scar agrees, and Miles lets him go, although Ed strongly opposes it. When they find out that Kimblee is near, to cover all of them, Winry then proposes herself to being used as a "hostage" by Scar to provide cover for the Briggs army and Elric brothers, and to secure herself from Central's grasp. Scar swearingly agrees to protect her, and Ed grudgingly accepts it. In the end, he goes together with Dr. Marcoh, May, Winry, and the two chimera soldiers who have chosen to defect from Kimbley's authority, guided by Yoki, through an unused mine tunnel under the city.

More recently, Scar has allied himself with Edward, Hohenheim, Mustang, Greed, Grumman, and Olivia Armstrong, the group leading the rebellion set to strike on the 'promised day'. In chapter 84, he shows incredible growth in his character by stating, although he is not here to save Amestris, he is here to change it and destroy the corruption, along with his tribe leader and most of the refugee village. Consequently, Scar has quite possibly developed the most of all the characters over the course of the series, as he was initially a serial killer but now works towards the common good.

Although quite harsh and cruel, Scar has an affinity for cute animals, similarly to Alphonse Elric. He seems to attract small children as followers, and is rescued by a child more than once.

In the compiled volumes of the manga, Arakawa draws her boss as a shadowy, angry version of Scar.

In latest volumes of the manga, his ability for destruction is often joked about in manga omakes, in which he is asked by an irritated Hawkeye (vol 14) to destroy a bathhouse who won't let people with large tattoos go in, and by irritated Alphonse (vol 15) to destroy a convenience store that won't let people with helmet/head protectors in. In volume 16, a spoof of Scar mutilating Marcoh's face and May healing it is shown, with the spoof resembling an advertisement for a plastic surgeon, claiming it to be the "Fullmetal Plastic Surgery Clinic" (in which Marcoh's face, instead of healed into a scarred, deformed figure, is turned into a handsome, bishounen-style face).

Anime
Scar is an Ishvalan, a group of religious people who take their name from the god they worship, Ishvala. In particular, the art of alchemy (known to Ishvalans as the "Grand Arcanum") was considered one of the greatest taboos of Ishvalan culture (as it implies that humans can better upon God's creations). Scar's elder brother Mattias broke this taboo by attempting the most dangerous form of alchemy, human transmutation, in an attempt to resurrect the deceased woman that both he and Scar had loved. As is the way of such things, the attempt failed (leading to the creation of the Homunculus, Lust), causing Mattias to lose his grip on sanity, and seek the legendary Philosopher's Stone, in hopes of successfully accomplishing his task. Realizing that the key ingredient in the forging of the stone was human lives, Mattias tattooed his body with the necessary transmutation symbols that would allow him to absorb lives and become a living Philosopher's Stone himself. The lives in question were those lost in a massacre of the Ishvalan people by the State Military, but as Scar and his brother attempted to escape after the attack, they were pursued by State Alchemist Zolf J. Kimblee, who used his alchemic powers to give Scar his eponymous disfigurement, and to blow his right arm off his body. Mattias dispatched Kimblee by robbing him of the power-enhancing Red Stone he was wielding, and then fused his own right arm to Scar's body before dying. Due to the type of Transmutation Circle on his brother's arm, Scar has a partial Philosopher's Stone always ready to be used.

Mattias's right arm bore the symbols necessary for the first two portions of an alchemic transmutation - the understanding of an item's molecular composition, and the deconstruction of that matter (with the third step being the reconstruction of the matter into a new form). Unaware of this particular detail, Scar traveled to the city of Central, in hopes of using the information in the State Library to discover the nature of the symbols. His entry to the library barred, Scar clashed with young State Alchemist, Edward Elric, who inadvertently tore his shirt and exposed his arm, causing him to flee. Not long thereafter, while ruminating in an alleyway, Scar was approached by Nina Tucker, a young girl who had been turned into a chimera by her father, and discovered the power within his arm when he deconstructed her body, killing her out of mercy.

Some background information about the symbol on the arm. Within the symbols on the arm are two statements of Latin origin, one running horizontal and one vertical. The statements are "dop la TERRA sie ca" and "TERRA A Ndan, colla" both using the main word "terra" which contains multiple meanings The earth/life/us/everything. These are statements describing the basics of alchemy and explaining that there is no way in which the laws of equivalent exchange can be broken. "dop la terra sie ca" in this context translates to "In the end everything will return" meaning that eventually everything will return back to the cycle of matter. "terra a ndan, colla" translates to "Life in Death, contributes" this is in reference to the philosophers stones nature in that in order to create the stone living souls must be taken and with every soul the stone becomes more powerful.

Now aware of the power he wielded, Scar embarked on a campaign of revenge against all State Alchemists over the course of the next three years, killing many by exploding their brains within their skulls. In tracking and killing the "Iron Blood Alchemist," Basque Grand, Scar crossed paths with Edward Elric (and his brother, Alphonse) once again, who attempted to prevent Scar from killing Tim Marcoh, another State Alchemist who had participated in the Ishval Massacre. The fight was interrupted by Major Alex Louis Armstrong, who held off Scar long enough for Elric and his brother to escape, but it was a brief respite - Scar soon tracked them down, and shattered Edward's arm, and a large portion of Alphonse's body. Reminded by them of his relationship with own brother, Scar promised not to kill Alphonse (as he was not a State Alchemist), but before being able to kill Edward, Marcoh confronted him with an incomplete Philosopher's Stone, which Scar's arm absorbed (as per its purpose to absorb souls). Unaware that this was the purpose of his arm (and that it appeared to cause him pain as it was absorbed), a suffering Scar fled.

When the Elrics later broke into the military's Laboratory Five, to uncover the twisted alchemic experiments that had been conducted there, Scar followed them, saving Alphonse from serial killer Barry the Chopper and battling the Homunculi Lust and Gluttony. When Edward was presented by the Homunculi with the chance to obtain a Philosopher's Stone by killing the prisoners held within the laboratory, he refused, and, noting this act of nobility, Scar held back from killing him.

Nursing injuries from this encounter, Scar returned to the refugee camp occupied by the remaining Ishvalans, only for it to be attacked by mercenaries posing as the State Military. Scar escaped with two children and an Ishvalan elder, and promptly ran into Alphonse once again, who was at the time separated from his brother after a disagreement. The younger of the children, Rick, was then captured by the mercenaries, and Alphonse and Edward reached an uneasy truce with Scar to work together and rescue him.

Through further study, Scar eventually came to realize the true nature of his arm as an incomplete Philosopher's Stone, containing the souls of all those who had died during the Ishval Massacre. Concluding that he needed the stone to stop the action of the State Military, he decided to finish what his brother had started, and traveled to the war-torn desert city of Lior and inscribed a gigantic transmutation circle around the city itself by dragging a rock through its dirt streets. Learning of his presence there, the State Military arrived in force, along with the Elrics, who feared that he planned to sacrifice all the inhabitants of Lior to create the stone. Once again, Edward and Scar battled, with Edward repeatedly transmuting the matter of his mechanical arm to prevent Scar from deconstructing it. The subsequent arrival and defeat of Lust delayed the fight, which was then halted by the arrival of Rose and Lyra, prompting the revelation that Scar, in actuality, intended to safely evacuate the inhabitants of Lior and use the invading military as his sacrifices instead. He also managed to clear Lust's thoughts on her past human life, and admits that he loved Lust's human form; he also claims to have loved his brother, but hated him for his negligence and ignorance.

Zolf Kimblee led a small army of chimeras into Lior, and with the evacuation nearly complete, Scar and Alphonse engaged him in combat, only for Scar to have his left arm be transformed by Kimblee's alchemy into a living bomb. Scar sacrificed his arm, deconstructing it off of his own body, to prevent it from exploding, and blasted a hole in Kimblee's chest. Kimblee, however, proved able to cling onto life long enough to transmute Alphonse's body into explosive material. Lust told him to wait for Edward's arrival, as the only way to save Alphonse was to transmute his body into a different material, which Scar lacked the knowledge to do. To save him, Scar transmuted his remaining arm, and all the power and souls within it, into Alphonse's armoured body. Finally, he got Lust to take Kimblee's dead body into the sight of the military amassed around the city, prompting them to attack. Suffering bullet wounds in protecting Lust, Scar used the last of his strength to complete and activate the transmutation circle around the city, dying as the transmutation took place, and the Philosopher's Stone was completed - within Alphonse, saving his life(since his body had now been transmuted into a different material). Scar's real name is never revealed, as he states that he no longer deserves one.

Last Words: "A Man who inflicts suffering can not rest. His guilty mind won't allow it. But today I can finally close my eyes to the living nightmare and lay down, knowing that I won't wake again. Brother..."

In the movie sequel, Conqueror of Shamballa, a parallel universe version of Scar is seen near the end driving a truck with Gypsies next to an alternate version of Lust, probably suggesting they developed a relationship in our world.

Alchemy & Powers
Scar himself is not an alchemist, and has very little knowledge of alchemist teachings. Scar's alchemy depends solely on his right arm's tattooed transmutation circle. His right arm was originally his older brother's (who was a skilled alchemist) which gives Scar the ability to use alchemy. However, instead of transmuting what he comes in contact with, he simply decomposes it into individual elements, completely obliterating the object (Scar's way of alchemy is often said as "stopping at the second step" without the final step of reconstruction) in the manga the reason is because he lacks the third part, which would be his brother's left arm, in the the anime it's simply because of his religion. This happens in both the anime and manga. In the anime, his arm is also an incomplete Philosopher's Stone which absorbs the souls of those he kills and gives him some subconscious knowledge of alchemy (for example, enabling him to recognize Nina's chimera nature simply by touching her).

However, his arm can't affect anything he doesn't know the composition of. Such was seen in the anime when he battled Gluttony in the library and in the manga when he grabbed Father and found his powers useless.

Techniques
Decomposition: Scar uses his right arm to transmute an object (or living being) and stops at the second step, deconstruction/decomposition, to break the object down into its base elements. Stopping at the second step allows him to use alchemy without performing a complete transmutation and violating Ishvalan teaching (although since Scar's arm only has the tattoo for deconstruction, he could not perform transmutations even if he wanted to). In the first anime, he usually uses this technique by placing his hand on a person's forehead and imploding their brains, blowing out the back of their skull. In the manga and second anime, he kills people by deconstructing their internal organs, tearing them apart from within. Also the color of his alchemy is different in both versions of anime; in the first anime, his alchemy is red while in the second anime, his alchemy is the normal blue.

Since Scar's alchemy can only destroy, he is often at a disadvantage during battles with State Alchemists, as he must get close to them in order to defeat them, while having no protection against their ranged attacks (he cannot create constructs or barriers of stone and metal like the Elric brothers frequently do). Usually he tries to overcome this difficulty by sending alchemic energy through the earth and deconstructing the ground beneath his opponents' feet, which causes them to lose their footing, giving him time to close the distance with his speed. He has also used it in other creative ways, splitting water in pipes into hydrogen and oxygen to create explosive clouds of gas.

Physical abilities
Scar has also proven to be quite strong and agile. He is able to match both Edward and Alphonse Elric and even Gluttony to some extent. In the manga, he is revealed to be an Ishbalan Warrior Priest, highly trained in martial arts. In a flashback chapter, he is shown to be able to defeat up to a dozen armed soldiers using only his hands and feet. He is more robust and powerful in the manga, easily defeating the chimeras in the tunnel with the alchemical powers granted by his right arm.

Trivia

 * In the first anime, Scar died without his name ever being revealed. However, the author plans to reveal Scar's name before the manga finishes (in the "extras" at the end of volume 15, Arakawa states she has a name for Scar, but it is a secret).
 * In the 2003 anime, Kimbly personally give Scar the X-shaped scar on his face and removed his arm. In the Manga, both injuries were caused by an explosion that Kimbly had caused.
 * In the 2003 anime Scar is much younger than he is in the manga and the 2009 anime adaption.