Game: Final Fantasy VII
What Makes Him Bad: Becoming one with the Planet and avenging his "mother's" death has always been Sephiroth's modus operandi.
What Makes Him Cool: We've all wanted to be as cool as "that" flame scene. You know the one.

What can we say about Sephiroth that hasn't been said before, hundreds of times over? Nothing, really—except he's always going to be the poster child for J-RPG villains everywhere. Flowing silver locks, bondage gear, and a sword that's more than a little overcompensating? You win, Sephy. And we're still going to draw all of that fanart of you. You can't stop us.