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.

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 transmutate 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 dieing 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.

In the manga
Greed is first seen in chapter 25, when Bido escapes from Edward and Alphonse. Later, in chapter 26 he orders Roa, Dorchet and Martel to capture Alphonse Elric. After chimeras capture and bring Al to Greed, he introduces himself and starts questioning Al about his empty armour. After short conversation, Al synthesizes stone fists to crush Greed. Surprisingly, Greed shrugs the hits off and throws Al to floor (Martel inside Als armour getting flung around). Greed shows to Al how to kill him, as Roa strikes Greeds 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 and fights against Greed. However, Greed proves to be harder opponent then Izumi thought and Alphonse agrees to make a deal with Greed. Izumi leaves Devils Nest to tell Ed about the deal. Suddenly, Führer King Bradley arrives with Alex Louis Armstrong and army unit. Afterwards, Edward goes to Devils Nest to meet Greed. Inside, Ed pays no attention to Als and Greeds suggestions about a deal and tells Greed that he has no interest in Greeds 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. 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.