In almost every movie, in almost every book, there is a scene towards the end that we all expect. It's the big scene where the villain reveals his or her reasons for all the evil behavior. I want to share something I have learned about this: the villain doesn't always have to have a motive. What? Yes. I know. This is not what we've been taught by Hollywood. But it's true.
During revisions for one of my manuscripts, an editor suggested simplifying my villain. I had made him bitter and complex, with a history that caused him to become this horrible person. Why not make him, well, just evil?
We've all heard it. Certain people are just bad.(Darth Maul, anyone? The dude killed Qui-Gon Jinn in cold blood.) That sounds so... prejudice, if that's the word. Sometimes, though, there isn't always a traumatic childhood or a death to make a human being want to hurt others. If your story is already twined with intricate plot lines and deep characters, consider making your villain the simple part. The motive doesn't have to be dramatic and significant. It can just... be.
Food for thought.