In my current work in progress I wanted my villain to have a backstory. Some of the best villains in literature and movies have had backstories: Darth Vader, Voldemort and others.
Villains, after all, have lived before we get to know them. While reading a few posts on villain backstory, some people argue that giving them backstories minimizes their sense of real evil. It almost requires the reader to feel sorry for them so the fear is gone.