In my own novels (and short stories) I always try to create villains with clear motivations, who from their point of view can justify what they do, even if objectively they are delusional.

I often like having a villain with an objective that is essentially the same as that of the protagonist. Lovely ironies can ensue. My gothic mystery novel The Irresistible Summons is an example.

Sometimes I even enjoy writing a story from a villain's perspective. This satirical piece, about a corrupt televangelist, is an example.