"I, Tiberius." 

Just kidding. Besides, they already made a movie about Caligula. I think the most depraved stuff is probably in history because there are things that most publishable fiction writers would find taboo to write about whereas a historian can squeak by on giving truly disturbing details, which is pretty much what Suetonius did.

When I think deplorable (and depraved), however, I think of the Julio-Claudian (Roman) emperors and their relatives, and it's hard to come up with any character I've played that anywhere approaches that standard.