If we're going for the craziest of the crazy evil, I'd have to say Joffery Baratheon from a song of Ice and Fire. Lets look at his stupid/evil resume: Note *Major spoilers here*
1: Killed Ned Stark for absolutely no reason and called it mercy
2: Had his guards beat up his wife to be(Sansa Stark), who was the daughter of Ned
3: Threatened to rape Sansa when she was married off to some one else
4: Tried to kill an innocent wounded kid, for absolutley no reason0
5: General stupid dickishness.
Seriously, if you want to find someone more stupidly evil you'd have to look at his insane mother.