Yes... I mean favorite bad guy from a video game. Not anything else.

And I say spoilers because to really know about a villain, don't you have to beat the game first?

Genre does not matter (but if I may be so bold, in my experience, only RPGs have bad guys with a personality).

Here is a run-down of all the big boys I can think of right now:

Kefka: my personal favorite from FF VI. Great nut-job. Cool theme song and the laugh vweee he he he!

Sephiroth: ...not such a fan of this one, but he does seem to be popular. I can't really remember what he was trying to do though. Sure, he killed Aeris...but Kefka wiped out towns (where you did not know anyones name though).

Sin: A gigantic watery ball is not a bad guy. And who is Yu-Yevon again?

Malak: Now THIS was a fun bad guy. Not only did he betray you, but he was also evil. Sweet. And he looked cool.

Krellian: from Xenogears. I really liked the character "If there is no God, I will create one with my own hands!" Nice quote...but not quite as much fun as Kefka.

Albedo: from Xenosaga I&II. Nuts, like Kefka...but I still don't really understand what his purpose was. Besides hurting MOMO.

Lavos: Chrono Trigger. He is a big evil rock. With a personality to match. Great game. Lousy villain (but his summoner was cool).

Okay, so those are my main ones right now.

Kefka is my favorite just because I think he is funny (running away and the 'son of a submariner' thing).

Azi