I don't do villains often enough. There are two approaches: give them sympathetic, reasonable motivations for doing the most unspeakable things, or get inside heads that are interestingly broken.
Sentiment: NEGATIVE
Both villains and heroes are a bit boring, really, unless they're flawed and broken somehow. If they're not flawed and broken, then clearly they need to be broken and made flawed. That's what an author does if he or she has any dignity.