Snadhy'rune, the closest thing Drowtales has to a Big Bad, fits a lot of the criteria for sociopathy/psychopathy. Her defining character traits consist of the list mentioned at the top of the page, and one person on the forum ran her through the Hare Psychopathy Checklist and found she hit nearly every point on the list, with the main ones she missed either covering periods of her life we haven't seen or that don't apply in context (i.e. drow do not get married so the "many short-term marital relationships" doesn't apply). She's effectively manipulated her lover Mel'arnach Val'Sarghress to be totally emotionally dependent on her to the point that when Mel's daughter is in a life threatening situation she freezes completely and can only say out loud that Snadhya will fix it, and it's strongly implied Snadhya views her as pet more than an equal. She keeps up a pretty effective Mask of Sanity for the public, but over the course of chapter 46 she gradually drops it until the absolutely cold-blooded way she murders her own daughter Kalki clinches it. Zhor also says that Snadhya's mother knew "the sickness in her daughter" which also heavily suggests that it's pathological.
Also Yuh'le, one of the Nidraa'chal, is explicitly referred to as a sociopath, but unlike Snadhya'rune it's much more obvious in her case, with her possessing a flat affect, severe Lack of Empathy and a habit of using her Blood Magic to make small animals explode for fun when she can't use it on other people, and was thrown out of her clan for a murder that it's implied she committed for fun. Contrasted with Snadhya she is a good example of a low-functioning sociopath compared to Snadhya's high-functioning. Also of note is how the Kyorl'solenurn Seers (who are basically The Empath and can sense the intent of others) are completely unable to sense anything from her and are enormously unsettled by this.
In Erfworld, Olive Branch fits this trope to a tee. She comes as close as the largely Grey and Gray Morality of Erfworld gets to being truly evil. Olive Branch is a charming Manipulative Bitch who inevitably betrays and destroys everyone around her. She is also a narcissist, having brought ruin to many sides and even the casters of her own side just to prove the superiority of her magic. According to Wanda, she is literally incapable of empathy or remorse and cares only about herself.
In Freefall, the first attempt at Uplifted Animals, chimpanzees, turned out like this; their frontal lobes were not developed enough to let them think through what they were doing before they did it. Dr. Bowman gets around this by being intelligent and self aware enough to realize this, and took precautions in advance to ensure he doesn't hurt people. This involved castrating himself with a plastic spoon.
Angel, the Villain Protagonist of The Good Witch, remorselessly torments and ruins the lives of her friends, family, and anybody unfortunate enough to cross her path with her newfound magic powers. There are hints she is a "made sociopath," not originally being so cruel and self-centered but gradually cracking under an intense amount of bullying, but any sympathy that might have been gifted to her has long since passed; for God's sake, she turns people into articles of clothing, which her unwitting mother then sells in her store, and keeps them sentient so that they can desperately try to find anyone to help them and eternally despair over their predicament!
Some fans of Ménage à 3 have referred to international lingerie model Senna as a borderline sociopath. She's certainly a narcissist, being vain, self-centered, and delusional; she also shows few signs of empathy, lies on a whim, possesses casual charm, and pursues all sorts of thrills. Given the nature of the comic, she's a fairless harmless comedy version at worst, though, and she does show flashes of some kind of fondness for Gary, along with deep and long-lasting feelings towards Sandra (though admittedly the feeling there is poorly-concealed hatred).
Tarquin is quite the sociopath — while his fans like to paint him as a leather pants-wearingNoble Demon, that doesn't change the fact that the lives of others mean very little to him. He "convinces" his wives to marry him. He forces Gannji and Enor to fight to the death because he thought Elan would enjoy it, simply because they had captured him and brought him to, the former after mistaking him for Nale (and seems confused when Elan isn't thrilled with the idea). He's also got Lack of Empathy down, as he tells Malack (his supposed friend) to stop whining about his dead "children" actually, it turns out, vampire minions and orders him to work with Nale (who killed said children). And then he stabs Nale, who is also his son, to death afterwards. It's quite evident that he sees everyone around him as plot devices, nothing more, nothing less. Which said, he apparently felt some kind of real friendship with Malack, he feels some kind of compulsion to bring order to the world, and he pales beside...
Xykon, the comic's Big Bad. At no point does Xykon show any feeling for another being that isn't merely practical (and sometimes not even then). He has little if any desire to control his impulses, possibly because unlike Tarquin he has the raw magical power to cow anyone into obedience or kill those who would oppose him, and is well-aware of it, so he never really needed to rely so much on manipulation. His motivation for committing evil can largely be summed up with "Why not?" He's easily bored and destroying the lives of others is his only method of alleviating the boredom. He's been like this since he was a child, when his pet dog died and he first awakened his magical power by raising it as an undead, then used it to torture and kill animals. As a teenager, he murdered his family in cold blood, simply because he knew he could. He is also far more cunning and manipulative than one might think; when sufficiently motivated, he can play others like a fiddle, such as when he tricked Redcloak into killing his brother. To top it all off, he is very charming and funny, as even Redcloak admits.
Penny and Aggie: Cyndi eventually turns out to be one. Initially, she comes off as a fairly standard Alpha Bitch-type, similar to Karen, and takes twisted delight in messing with Penny, Aggie, and their friends. This reaches a head when she manipulates Stan into destroying his relationship with Brandi and is positively gleeful about it. She eventually cements her status as this by the end of the Missing Person arc. Right before the police rescue her from her kidnapper, Charlotte, Cyndi appears to show some remorse, and convinces Charlotte that they are Not So Different. When Charlotte slits her own throat in grief, Cyndi reveals that she had already managed to free herself, and that her Heel Realization was just an act to get Charlotte to kill herself. Finally, after she is rescued, her parents reveal that the police managed to hack into her laptop during their search for her, and discovered her disturbing diary entries about how much she enjoys making other people suffer. They then tearfully apologize to her as they commit her to a mental hospital.