All in all, my nostalgic answer would be the Master.
Myrkul in Mask of the Betrayer was a delicious bastard. The Founder could also be considered a villain in some sense. Part of why that campaign works so well, gives you the chance to react to the characters (though Myrkul is always a dick).
Since it's fresh in my memory, Gaunter O Dimm in the Witcher 3 is quite good. Creepy, scary yet charismatic in a way. And with that lovely feeling of there being a lot more going on besides what we see in the story in the game.
Myrkul in Mask of the Betrayer was a delicious bastard. The Founder could also be considered a villain in some sense. Part of why that campaign works so well, gives you the chance to react to the characters (though Myrkul is always a dick).
Since it's fresh in my memory, Gaunter O Dimm in the Witcher 3 is quite good. Creepy, scary yet charismatic in a way. And with that lovely feeling of there being a lot more going on besides what we see in the story in the game.