Oh yeah, there's a whole category of 'bad guys' out there who, with a tiny subtle tweak, I think would make great lers.
Joker--he's got the sadistic streak, now if we could only turn off the homicidal mania...
Mystique--She's got the personality for it, for sure. I'm not even sure this would be all that out of character >.>
Harley-- definitely would make a good 'ler. Again, not even out of character, and she'd just have fun with it.
Catwoman--slinky, sexy, and controlling. She'd make a total domme!
Seto Kaiba/Pegasus(From YuGiOh)/many many anime 'villains'--Y'know that class of villains that's sympathetic, not really evil but is loud, taunting, and takes a great deal of pleasure in outwitting the protag? Yeah. Them. Bonus points if they become a good guy later.
Nathan Wallace the Repo Man (Repo: The Genetic Opera)--for those of you who don't know this one, he's basically a government owned hitman. He's a little crazy but deep down he's a good man (and teeechnically kind of the protag)--if the relish he takes in doing his 'duties' could be switched to something a bit more playful? Magic.
My brain's not doing so well right now because tired, so I can't think of more x) I can guarantee I'll be back to this thread o/
~K