Gluttony

is the second homunculus to appear in the series, typically being in the company of Lust. He is a large, simple-minded homunculus whose thoughts rarely stray far from eating. He has powerful jaws, acidic saliva, and can and will eat almost anything. He particularly likes eating people, and the only way he can find enjoyment in a battle is if he can eat his opponent afterwards.

In the anime
After Lust's death, Dante transforms Gluttony into a mindless eating machine, an act that ultimately backfires when he eats her. He appears again in Fullmetal Alchemist: Conqueror of Shamballa, having transformed into a large, multi-limbed monster since his appearance in the anime. He exclusively attacks Wrath during the movie, giving Alphonse Elric an easy opportunity to use Gluttony to create a gate to the other world.

In the manga
Gluttony is the failed product of Father's attempts to create a Gate of Truth. When activating this gate Gluttony's stomach opens up, revealing a large eye at its center. His ribs spread out to act as a border for the gate, and then double as large extendable teeth. With these teeth Gluttony can consume everything in his eye's field of vision in an instant, which is then transported to a realm within himself. Artifacts from centuries before the start of the series can be found there, indicating Gluttony's age. Gluttony tries to use this form to kill Roy Mustang, Lust's killer, though he makes the mistake of eating Edward Elric and Envy instead. Hoping to make it up to Father, Gluttony takes Alphonse Elric to see him, where Ed and Envy are able to escape to. In the ensuing battle Gluttony runs out of energy and he is no longer able to revive himself. Father takes what remains of his Philosopher's Stone and restores him with all his memories intact.