I'll have to hand it to AGD. The Father wins it. He's Graham's evil counterpart. The Father has his "family" of Evil with its poisonous claws spreading all through the world, and Graham's Lawful/Neutral Good family has to answer that threat. AGD introduced him as an ancient and vague threat from Daventry's beginnings who has been running a thousand-year Xanatos Gambit to gain power - possibly destroy creation with it. Worse, Graham didn't pick the fight - Graham just happened to be standing between The Father and whatever nebulous goal the b*stard has. First, he infiltrates Graham's armies. then, he sets Graham up to head to Kolyma, and into a trap. Graham manages to dodge the trap, expose "Gervain," and duel him to defeat...only to have The Father emerge from his guise and throw the final strike in the form of a curse.
AGD then depicted him as using his network to try and break Graham and coming VERY close to doing it - orchestrating the destruction of Daventry via the three-headed dragon, arranging Alexander to be brutally enslaved, and leaving Rosella behind as a thread of hope...only to have the dragon demand her life. Even though Alexander manages to escape, slay the dragon, and free Rosella, the curse is still in effect - and having been brought from despair to joy in the space of hours, he is felled by the curse and comes within a hair of death. Though Rosella thwarts the second part of the curse, and the third part...doesn't quite work as the Father intended, the monster is not defeated and will not be defeated. He will likely outlive Graham and find another king that isn't as resourceful in order to try again...
Canonical? Alhazred. At introduction, he comes across as an arrogant jerk with a lot to hide. When we figure out that he was behind the islands' discord, he's already jumping up to "power-hungry slime bag." When we find out what he did to Cassima's parents, he turns into "dangerously nasty power-hungry slime bag." It gets worse when we see that he was in league with Mordak. When we realize that he plans to "dispose" of Cassima after the wedding night (read: rape her first)? Alhazred has crossed the line on so many levels and in so many ways. I don't even think we saw the full extent of what he was capable of or what else he may have been up to. If he turned out to be a low-level sorcerer or alchemist - that just makes him worse for the same reason Tarkin was a nastier piece of work than Vader. You cannot blame the Dark Arts for addling his mind; he's plenty evil as is.
Giving him a run for his money is Lolotte. Seriously, the b*tch has a torture chamber in her castle. There are at least two poor souls who met a slow, painful end there, too! There's her assault on Genesta, of course. But it's her cool, manipulative demeanor that makes her very creepy. She's in charge, and knows it. I keep trying to think of the kind of mind games she must have played on Edgar and cringe. She kidnapped him, warped his body, and tried to shape him into...who knows? All we know is that it didn't seem to work, because he turned out to be a decent guy. And the fact that Edgar or her mooks didn't seem to grieve overmuch for her says plenty.