If you're an overachiever who doesn't mind being at the top of the most popular "bad guy" list, then there's really only one choice... Hitler.
Pros: He's probably the most infamous historical villain (at least in America), he had an entire nation almost hypnotically under his thumb, and he's undoubtedly still idolized today by some.
Cons: Well, these should be obvious and apparent. Don't think I should have to mention them.
