Some of the characters I’ve created are truly disturbing (the best villains are). My villains can be subtle and complex or outgoing and terrifying. I spend quite a bit of time thinking about who they are and the motivation behind their actions to make sure they’re as three-dimensional as the protagonists.
I’ve found that I’m much more comfortable writing monstrous villains than human ones. Give me a spider-headed zombie over a human antagonist any day. It’s much less frightening to think about giant multi-eyed grub worms that I seriously doubt exist (at least, I really hope not!).
While writing, I need to keep in mind the reason I have villains in the first place: to give my protagonists something to overcome. I’m not interested in writing detailed accounts of a vampire’s descent into madness. That doesn’t mean I don’t think it through outside of the pages of my books. Knowing the villain’s history and motivations adds depth to the story, but in the end, my books are tales of love and triumph.