I just checked out my Dark!Doctor blog, as that muse went on hiatus too the past few months, and realized he isn't a great villain. When I first roleplayed him, I made him calculated, fearless, clever and above all with bloodlust. After that, I found he wasn't scaring me. I wanted to write about someone that even frightened me, his writer. So I revamped him to be both broken, dark and mad. He acted on impulse, had several disorders that forced him to hurt himself and resorted to eating humans and the most sickening torture I had even thought of. But now that I've taken a step back, I see he isn't what I'm looking for. He isn't a true villain.
I want to create a Doctor that sends chills down ones spine, but I don't know how to accomplish that. I want him to be an original dark Doctor; most of the dark Doctors on this site -though they are all amazing and perfect- are the same class of calculated, threatening, evil Doctor. So I decided to bring this question to you: what makes a villain work? What would be the most frightening, most chilling kind of Doctor?