Greed
Greed is a Homunculus known as the "Ultimate Shield," and he lives up to the name—his whole thing is that he can rearrange the carbon in his body to harden his skin to diamond-level toughness, making him basically untouchable in a fight. As you'd expect from someone literally named Greed, he's obsessed with luxury and power. He surrounds himself with loyal minions and beautiful women, loves expensive living, and isn't shy about flaunting it.
What's interesting is that beneath all the avarice and swagger, he genuinely cares about the people who work for him. Fans often note this softer side as one of his most compelling traits. He's also known for casually flipping people off in the manga—a habit that's stuck with him across versions.
His character varies pretty significantly depending on which continuity you're looking at. The 2003 anime takes him in one direction, while the manga and 2009 anime adaptation portray him differently.
Content compiled by AnimeList.moe from publicly available sources.