Cornello

Father Cornello is a minor antagonist in the Fullmetal Alchemist series. He was a charlatan and the founder of the Church of Leto in the small desert town of Reole in Eastern Amestris. As such, he devotes a great deal of time and effort building up a legion of followers in the town as a type of cult leader through the work of divine miracles.

His Part in the Story
The Elric brothers Edward and Alphonse discover, soon after arriving in Reole, that Cornello's 'miracles' are nothing more than alchemy augmented by a Philosopher's Stone that the priest has in his possession. Cornello himself admits that his motivation for doing so is to create an army of religious fanatics large enough to overthrow the Amestrian government and place him as the country's ruler. Ed confronts and defeats Cornello (while revealing to the townspeople that the priest has been duping them), but during the struggle, the Philosopher's Stone is shown to be an imitation and inflicts Cornello with an alchemical rebound that deforms his hand.

As the furious people of Reole march on the church and demand an explanation from the priest, Cornello rushes to Lust, who had given him the stone in the first place. As Cornello has outlived his usefulness to the Homunculi, Lust kills him and the corpse is eaten by Gluttony. After which, Cornello is imitated and effectively replaced by Envy, who plans to stir the townspeople to war, with the Letoist fanatics brutally attacking the skeptics and vice-versa.

Differences between adaptations
During the 2009 anime, it is shown that despite being injured with a rebound, Cornello is able to use the stone's power to morph into a gigantic and monstrous version of himself. But in both the manga and 2003 anime, he is defeated in his normal form almost immediately after the rebound renders him practically useless. It is unknown whether or not Lust killed him in the 2003 anime, as it is not shown, although it is implied, as after he returns to Lust, Gluttony asks if he can eat him. After which, the scene cuts to black and we hear sounds of Gluttony feeding on something, presumably Cornello.

Trivia

 * The reason Cornello is killed in both versions of the story is because he would be unable to regain his followers' trust; not mention his lack of knowledge of alchemy meant he couldn't heal his arm from the rebound, which would serve as proof of his trickery.
 * Envy was brought in to replace him since it could easily manipulate humans through charismatic speeches and not need fake miracles.
 * Curiously, Father Cornello's manner of dress-- black jacket with high collar that has a thin piping around the collar and down the front portions and silver closures, over black trousers-- is rather similar to Edward's general clothing, with the exception of Ed's familiar red coat.
 * Although Cornello is one of the few villains to not actually directly accuse Ed of being "just like" him (as so many other villains throughout the series tended to do), he does imply it by referring to Ed's desire for the Philosopher's Stone and, in the 2009 series, his willingness to include Ed as a conspirator in his plan to take over Amestris (offering to carve a piece of the country out for Ed).
 * The reason he is a puppet of the homunculi differs between anime.
 * In the 2003 series, it's implied he was being used to lure alchemists Dante could use to make a true philospher's stone.
 * In the 2009 series, Cornello was supposed to start a riot to lure in the military to carve a "crest of blood" in the Nationwide Transmutation Circle.