Bad guys whose sole motivation is "to do bad things" annoy me. I've seen a lot of them over the years--more often in movies than in books. Whenever I encounter them, their unidimensional phoniness kicks me out of the story. They offend me--both as a writer and a psychologist.
If you're a writer, you need to make your characters believable.
Even the villains.
Especially the villains.
What motivates your bad guy? Greed? Revenge? Fear? Even if your villains are insane, their actions need to make sense from their own world view. The crazy homeless guy waving his arms and running down the street does it because he sees bats the size of house-cats flying at his head. They are absolutely real to him. Motivations don't have to reflect reality--they have to reflect the character's reality.
I'm revising book three of Ganzfield right now, and I need to make my bad guy's motivation clearer. It looks like revenge, but it's really fear. There's a desire to "monologue" here--the movie The Incredibles mocked that beautifully--and simply let the villain share his evil-plot-to-rule-the-world when he believes that the MC is helpless and about to die.
When in doubt, try writing a few scenes from the villain's POV. It's quite illuminating. You can also check out Gregory Maguire's Wicked or Joss Whedon's Dr. Horrible's Sing-Along-Blog, if you want to see the great ones build "sympathy for the devil."
To put you on the side of the angels today, though, check out these charity fundraisers that run through the end of May:
Brenda Novak's Auction for Diabetes Research
My book trailer for Nothing But Nets
Yes, I know there's a problem with my homepage (not Ganzfield.com; that's fine).
Network Solutions is trying to fix whatever's wrong, FTP-wise.