Note: Just because I'm listing these evil dudes and dudettes, it doesn't mean they're in. These are just here to get y'all thinking, because these villains could be from anywhere!

The Joker
Hades - (Disney's Hercules)
Darth Vader
Voldemort
Treize Khushrenada
Lex Luther
Apocalypse - (THE Apocalypse from... uhm... DC AND Marvel?)
Cthulhu
Sauron
Maleficent
Sephiroth
The Borg
The Headless Horseman
Smoking Man - (X-Files)
Eric Cartman