Greed

(Japanese:グリード, Gurīdo) is a greedy Homunculus, most known as Ultimate Shield, as he can change the density of his body to that of the carbon, being weak as graphite or hard as diamond. Like his name, he is very greedy. He also has a habit of flipping people off in the manga.

Manga
Greed first appears as having rebeled against the homunculuses, now hiding in the Devil's Nest in Dublith, with his chimera gang. After learning of the Elric's brothers battle with Scar, he becomes intrigued with the notion that the youngest brother, Alphonse, is a suit of armor with soul-attachment. Contrary to fact, he believes that having a soul attachment would make him immortal. He sends out his smallest member, Bido, to confirm his suspicions. Bido finds them in Dublith, where he barely escapes the two.

His hopes confirmed, he orders the rest of his gang Roa, Dorchet and Martel to capture Alphonse. After the chimeras capture and bring Al to Greed, he introduces himself and starts questioning Al about his empty armour. After a short conversation, Al synthesizes stone fists to crush Greed. Surprisingly, Greed shrugs the hits off and throws Al to floor (with Martel inside Al's armour getting flung around).

Greed shows to Al how to kill him, as Roa strikes Greed's head to pieces with his hammer. In seconds, Greed rises up with no wounds, explaining that he, in fact, is Homunculus. Some moments later, Izumi Curtis storms in to rescue Alphonse. She quickly gets in a fight and finds herself outmatched. After she is beaten, Alphonse agrees to make a deal with Greed. Izumi leaves Devil's Nest to tell Ed about the deal. Suddenly, Führer King Bradley arrives with Alex Louis Armstrong and an army unit.

Afterwards, Edward goes to the Devil's Nest to meet Greed. Inside, Ed pays no attention to Alphonse's and Greed's suggestions about a deal and tells Greed that he has no interest in Greed's plans and demands him to free Al. Dorchet tries to defeat Ed but gets beaten in seconds. Seeing what Ed is capable of, Greed fights Edward alone. After getting his neck broken, Greed changes to his completely armoured form.

Greed quickly defeats Edward, who suddenly gains the upper hand against his ultimate shield. Before the two can finish, though, an army unit storms the Devil's Nest. Greed is quickly able to escape, with Alphonse still in his custody. However, in the sewers below the club, he is met by King Bradley, who is actually Wrath. Not knowing he is a homunculus, Greed quickly under-estimates him. In a matter of minutes, Wrath kills all of Greed's gang (except for Bido), Greed is captured and Alphonse is rescued.

Shortly after that "Father" melts Greed. Ling is then transformed into the new Greed after being spat out of Gluttony's fake Gate Of Truth.

In the anime
The second oldest of the Homunculi, Greed was created by Dante. Greed was killed by Edward Elric after he figured out how to transmute Greed's body structure, allowing him to pierce Greed's heart, killing him due to all the Red Stones previously leached out of him. Before dying Greed told Ed how to weaken the Homunculi.

In the OVA "Reflections", a segment possibly reveals Greed's past and the reason he broke away from the rest of the Homunculi. A voice-over by Envy stated that Greed was Dante's former lover and the current him still loves her. Envy goes on to state Greed was merely an experiment. He denies being some love-struck fool and storms off in a huff.

In the same segment, Greed states that Envy always did like to torment him, so the story could actually have been a lie. But seeing how even though he was dying, Greed didn't inform Edward Elric of Dante's involvement with the Homunculi; and the fact he backed down from harming Edward when he noticed Dante was watching, Envy's story could actually be true.