I am a huge sucker for villain monologues and an even bigger fan of "bad guy stops being a bad guy to help fight even badder baddie" (whoops that's a lotta bads) and a plus when they defeat bigger villain only to try and fight the hero right after. It may be a bit cheesy (or not cheese does taste good) but it interesting to see other people's takes on it
I also like sassy villains and a good ole anti-hero (do people still have anti-heroes? aside from the popular ones that is)
ah and the "sweet character who's actually not so sweet" or "scary character who's really a teddy bear"