Little about Llan:
He is opener of the way for all the evil that lurks outside
1. http://i31.photobucket.com/albums/c365/A_Flight4/AlphaFlight72-03.jpg
"Llan being the next worse thing to the devil himself" and Llan isn't a demon or a god, something far worse
1. http://i31.photobucket.com/albums/c365/A_Flight4/AlphaFlight72-09.jpg
"The Sorcessor is the most powerful of the anicent evils. He is the architect of madness, the bringer of despair"
1. http://i31.photobucket.com/albums/c365/A_Flight4/AlphaFlight72-20.jpg
I don't see Dr. Doom as being really like, one of the most evil men out there. One of the best villains, definitely, but he shows that he's not 100% evil sometimes. Same thing goes for Venom, and even Galactus. I would assume that, out of the more mainstream people, Thanos would get my vote cause I don't know of any instances where he's backed down from an evil persona, but Mephisto probably would be #1 if the guy is supposed to be the equivalent of Lucifer basically.