Xykon is funny, charming, easily bored, and probably the sickest character in The Order of the Stick. In Strip 448, he makes the entire Sapphire Guard kill each other with a Symbol of Insanity, just to show Redcloak it would work. In Start of Darkness, he's even worse - Rich Burlew states in the opening that he tried to tell the story without making Xykon the slightest bit sympathetic. Most would agree he succeeds. Although Xykon does get a sympathetic moment - which lasts for all of two seconds. On the very first page, Xykon's dog has died and he, a four year old child, sobs like anyone would. He then uses the power of Necromancy to revive his dog and uses him to kill a bunch of birds...yeah. Xykon's been compared to The Joker in being a villain who is both despicable and horrifying, and yet arguably the most entertaining character.
The "hypothetical offspring of Cruella de Vil and Sauron" has evil measured 4.5 kilonazis and is used by the Lawful Good afterlife as a baseline of evilness.
General Tarquin presents an interesting experiment related to this trope - an attempt to see how many times a likeable character who really has a good side (he really loves his family) and motives people can understand can cross what would be the Moral Event Horizon for anybody else before people will agree that he is a Complete Monster. He keeps commiting atrocities that would send anybody else straight into this page but still remains a sympathetic character.
Jack gives us Drip Tiberius Rat, the sin of Lust, one of, if not the most, vile webcomic villains ever, whose lowest point was raping a small child to get revenge on the title character (said child being one of Jack's only friends). The real kicker? It was Drip's son. And he knew it, too. In fact, that was the reason he was able to do it, because only those related to the kid could actually harm him.
The rest of the Sins, excluding Sloth, get pretty close. Sure, Jack was a mass murderer who quickly climbed the ranks to successfully driving the entire human species to extinction over a Dead Little Sister, but at least he's somewhat sympathetic compared to most of Hell's denizens. Sloth, we just don't see do much.
In The Powerpuff Girls, Him is actually already pretty bad, but in Grim Tales, it gets ridiculous. The fact that when he cut off his own daughter's hands so that he could replace them with claws was the least of his crimes is an indicator. He also tortured said girl with every horrible experience he knew of in the ultimate Break the Cutie. He had Minimandy nearly kill her brother with More than Mind Control, afterscrewing with their heads. When Him got betrayed by Her, he got really mad, which is understandable. But he later said he's mad not because of what she did but why she did it - to save her friend, telling her that if she did it for completely selfish reason, he would actually be proud of her, but the Power of Friendship is just disgusting to him. Could see that coming, since he's Satan. Now that he's free from the shackles of cartoon censorship, do you honestly expect himto notexploithis creative freedom?!
Mandy herself is considered a Complete Monster since she's directly responsible for 9/11, the 2004 Tsunami, and Katrina...all just to get Grim back on his feet.
Recent strips seem to strongly suggest that Mandy is also responsible for the destruction of Megaville and the death of future versions of the Powerpuff Girls Doujinshi cast, also known as her friends. Not even her own children are safe, as she beats Junior for defending Mimi. Even Grim was appalled by what Mandy has done.
Oogie Boogie from Nightmare Before Christmas is already a monster in the film, but he took a level in evil when he torn Mini-Mandy apart.
Dark Danny from Danny Phantom apparently has also gotten even worse than his original version - even Mandy seems to tolerate him only as long as she must, which is enough to get pregnant with him to create the strongest of her offsprings. And he lets her keep the baby only because he is confident it will be raised to be an even bigger Complete Monster than him. There are also some unplesant implications about what he did to Danni.
The fanbase seems to want him to meet with a slow, painful end.
Silver, Big Bad of The Law of Purple, masterminded the plot to murder his entire extended family (which happened to be Caligula's Royal Family) in order to erase the stain of his cousin Blue's birth from the bloodline. He's since begun work on "purifying" Caligula as a whole using similar methods.
Trace Legacy from TwoKinds used to be this before he got amnesia. This page should be proof enough.
Advisor Toh in Blade of Toshubi enjoys torturing and breaking women. He also has a room filled with the tails of the people he has killed (including his women) that he occasionally stuffs his women into for extended periods, sometimes for punishment, but sometimes For the Evulz.
There's also Major Kohi, who is by far the most sadistic Feline soldier we've seen so far.
Interesting example from Mind Mistress. First, we have pedophile and murderer Les Kidman, who fits this trope perfectly. Then we find out that Lolerei's grandfather (who appears only in retrospections) hired him as a part of a plan in which he was supposed to kill her. Why? Because Lolerei is mentally challenged and her grandfather considered it a disgrace to the family name.
In the published webcomic Trace, a scientist who became a trace follows this path very shortly after.
Same goes with the creepy child, since it is somewhat apparent that he is causing a good portion of the problems in the story.
In El Goonish Shive, Damien stands out among the other villains because of just how seriously he's played. Other villains are competent and frightening in their own way, but they all have a Freudian Excuse or some other qualifier that allows the audience to empathize with them. None of that applies to Damien. He constantly hits and demeans Grace and her brothers, believes himself to be a god, wants females for his operation simply so that he can breed more shapeshifters for his army (the only reason he's interested in Grace), and slaughters anyone who stands in the way of his goals. What separates him from the other villains is that he doesn't even get to be funny. Every strip he appears in will be dark and serious, guaranteed. The author killed him off for this very reason. He didn't want the strip to develop Cerebus Syndrome as a result of Damien's presence.
Kore, a dwarven paladin and Knight Templar with a very polarized view of good and evil. He views evil as a seed, and any who could potentially harbor that seed must be eradicated without mercy. He crosses the Moral Event Horizon in his first appearance when he murders a dwarf child off-panel, for the 'crime' of being an orphan and being raised by an orc merchant, which could have led to the child having sympathy for the monstrous races and therefore increasing the potential for evil in the world. His status as a paladin is one of the comic's biggest mysteries; because he never demonstrated paladin powers in his early appearances, many fans assumed he was a fallen paladin who'd lost his powers for his frequent displays of evil behaviour. Then he finally did demonstrate a paladin power, healing Chief...in order to keep him alive while torturing him.
Dellyn Goblinslayer, ranger and captain of Brassmoon city's elite guard. Highly sadistic Torture Technician and fantastic racist whose hobby was capturing live monsters, then vivisecting them in order to learn their weaknesses. He also had a Yuan-Ti slave named Kin, who he raped and beat on a regular basis. Kin's revenge on him was anything but pretty.
Mryorg the Ogre, who appears in the backstory of The Axe of Prissan. Having had dealings with demons since a young age, he forced a captive demon to carve a rune on his chest. The rune gave him the ability to communicate with demons and make occasional journeys into the first layer of hell; in return, these journeys burnt away his ability to take pleasure in anything except the suffering of others. Learning of the Axe of Prissan, an artifact used to bind a powerful demon, he sought it out solely so he could release the demon from its prison; when he aquired it, he went on a rampage and butchered many good creatures, in a time that paladins call the 'Time of Dark Fire'. Eventually, he gave the Axe to a paladin, not out of any kind of remorse, but simply because he decided that knowing the demon lord was suffering from being imprisoned gave him more satisfaction than the suffering the demon would unleash by gaining freedom.
Psion!Minmax raises some controversy. He expresses honest regret for the atrocities he commits, truly believing his victims will be better off when he's done. While, by the letter, this disqualifies him from the trope, the sheer brutality he displays while maiming and killing alternate!Kin and Forgath (as well as the fact that he's done so several hundred times now) is so over the top, many people find him fitting this trope in spirit, if not letter.
Mob Ties has Bengal, who is a rapist, murderer, and freakin' god of undeath confined in a human form. Among his many sins, he has raped Mika, who was 13-14 at the time, murdered Mika's best friend Kyoko, and then destroying the one object that might have undone that murder. He also killed Santa Claus.
Erfworld has Wanda, who, if not already there, is approaching the Moral Event Horizon at close to lightspeed. She will stop at absolutely NOTHING to have more power and control.
All Erfworlders are bound by a metaphysical principle called Loyalty, that binds them to their side and acts as a kind of supernatural resistance to any attempts to sway them towards betrayal. The above character has explicitly stated (and demonstrated) that their only Loyalty is to Fate itself, having betrayed and slaughtered entire kingdoms in order to help fulfill prophecy.
Dead Of Summer gives us Alan Stone. In flashbacks, it's revealed that he subjected zoo animals to hideous experiments, already giving him quite a few negative points. After beating the tar out of a sympathetic character and kicking him and the main character out into the dangerous, zombie-ridden city, he finds out his wife has been working on a cure for zombiism by testing it on a monkey she adored. His reaction? TEARING OUT THE ELECTRODES TO ITS BRAIN.Then he injects himself with the 'cure', turning into a literal monster. And then he injects his wife with it, turning her into a zombie. And his wife was pregnant. After all that, he injects the remaining zoo animals with it to build an army of the undead.
The Seer on Kid Radd. Essentially, he's a virus that didn't go off on the day it was scheduled to because he realized that humanity would survive. He spends the entirety of the comic finding a way to get a sprite body, then a physical body, so he could kill everybody in both worlds. The kicker? He didn't need to do any of this. He could easily kill both populations at any point, but wants to be there physically so he can see his victims cower in fear of him before he slaughters them. Then, once he was done with Earth, he planned to search the galaxy for other forms of life just so he could go on killing for eons. Radd probably summed it up best.
Radd: Dude, you are the sickest thing on the internet. And that's saying a lot. The Seer: Blame my creator...I think I'll thank him personally before I kill him.
Cuanta Vida. After Red was killed, he was replaced with Rojo, who despite being seen as badass at first, soon crossed the line into complete monster-hood when he cut out BLU Sniper's eyes, driving him to suicide. Just in case people weren't sure how rampantly evil he was, he then cut off BLU Engineer's hand. And neither does he seem too fussed about the idea of killing RED Sniper, his own teammate, just because the guy didn't want any part of Rojo's scheme for the BLUs. Only time will tell what horrors he'll commit next...
In Girl Genius, Lucrezia/The Other qualifies for this trope on the basis of enslaving and slaughtering many thousands of innocent people, betraying the world's greatest heroes, and being the worst mother ever - killing her own son, using her own daughter for a Grand Theft Me, and then plotting to kill said daughter when that plan goes badly awry. She shows no remorse or sympathy for anyone other than herself, whether they are a victim, an innocent bystander, or one of her own loyal minions.
Most of the old Heterodynes are implied to fall into this trope, having been described as "a family of monsters so fearful they were only spoken of in whispers". Special mention needs to go to the family patriarch, Prince Clemethious, who is said to always smile "for he dreamt each night of new horrors to unleash upon his hapless enemies". His eldest daughter also deserves a shout-out, turning the king that defeated her father into a wolf and riding him into battle, laughing in triumph.
Susan from Sire. You might be inclined to think of her cruelty to Anna as the frustrations as a lonely child. That is, until she savagely beats in the head of the only person who cared about her, simply because he didn't shower her with enough attention. After this, she pins the rap on Anna, laughs off her suicide attempt, snaps the neck of her lawyer, smuggles herself and Anna into another country, and leaves her at the hands of some unsavoury types. And while she's doing all this, she coerces Anna into thinking that it was all her fault.
The Infernomancer (known by some as TIM) from Dominic Deegan. Even by the standards of a demonically empowered murderer (yes, there are more than one of these in the comic), TIM is a sick piece of work. In an early story arc, he tried to find the headmaster of the local magic academy (Dominic's mother) by attacking the school and slaughtering students until one of them coughed up her location. Unbelievably, he topped himself after becoming the servant of an Eldritch Abomination — after escaping limbo, he celebrated his freedom by massacring random places of worship. Then he wiped out a village for kicks — that Dominic's brother was also there was just a bonus to TIM. It doesn't help that TIM is essentially unkillable — banishing him to Hell didn't work and actually made him stronger. Banishing him to limbo didn't work either — and again, it made him stronger.
Mordecai Heller, the Obsessive-Compulsivehitman of Lackadaisy Cats. His OCD arguably makes him even more of a monster - he once killed his getaway driver for sneezing too much. He launched into a terrifying tirade against a man he was going to kill because his position in the backseat upset the symmetrical balance of the car. Mitzi mentions that, when the Marigold gang gave him a better job offer than the one he had, he kneecapped Viktor, his partner of several years, on his way out the door.Perhaps worst of all, certain lines of dialogue indicate that he may have had a hand in the death of Atlus May, his previous boss and Mitzi's husband.Word Of God has actually stated that Mordecai has no morals whatsoever.
Cyndi from Penny and Aggie. A manipulative sociopath who almost gets off on driving people to suicide. In a really creepy and incriminating file on her laptop, she documented how fun and easy it is to dig a hole into someone's psyche and widen it. She brags about nearly driving Michelle into starving herself to death and she had plans to destroy Daphne and Sara's relationship in the hopes of getting one or both of them to commit suicide. In the same strip this was all revealed, she successfully goaded Charlotte into slitting her own throat by using her Mommy Issues against her. Seeing someone bleed out in front of her thanks to her words puts a grin on Cyndi's face. What's even more damning is that both her biggest "success" so far AND her next intended victim, who she merely considers "practice" (Meg), are erstwhile members of her own clique from the "Popsicle War" arc. What an utter scumbag excuse for a human being.
Avogadro Pompey stands out as a Complete Monster even compared to the Jerkass cast of Something Positive: he kept Pepito as a sex slave, psychologically and physically abused his nephew, and set Kharisma up to take the rap for a murder (his own, as a matter of fact) which she didn't commit.
In Everyday Heroes, Wrecking Paul appears to be just a typical Big Guy, until we find out that he is a serial killer. He specifically chooses locations where women will be present and always hires female sidekicks so that, if his regular target isn't available, he can turn on his own teammate.
Samurai Princess's Fawdry qualifies after nonchalantly blowing a hole in Itchyknee-san's head and laughing about it.
In The Abominable Charles Christopher, we don't even see him, but a human member of the circus definitly counts for what he did to moon bear:
Ha! You must treat each of life's problems with its own solution my friend. The little bear cub... When we took her, she cried, and cried, and cried, and would not stop. I cut out her tongue, and now she is silent. You see? Every day we learn something new.
Derek, a magic user who would force other magic users (usually girls, apparently) to turning themselves into statues which he then collected (he got what was coming to him, though).
The "Messenger of Death" arc involved a killer shaman hunting other shamans by plunging them into absolute nightmares.
Jack Noir of Homestuck goes from a corrupt, petty little bureaucrat to an all-consuming force of destruction over the course of the story and probably ticks off every trope related to murder on his bloody march across creation. But what really makes him reprehensible is a brief glimpse into his viewpoint that reveals he doesn't think anything of all his murders and only slaughters people because he believes it's the only worthy form of entertainment for him now. Even then, he barely takes any pleasure in the havoc he wreaks and takes a few moments after killing the two protagonists' parents to moan over how bored he is. It's like Evil Is Petty on a cosmic scale.
Granted, the only thing that really changed is that he got superpowers. His troll equivalent, Spades Slick, is just as single minded about murdering everything he comes across and only forms alliances to reach his own goals (namely, exiling the Troll's Black Queen, who later becomes Snowman), and when we see him again, his first instinct is to wail on Doc Scratch's head with his horse hitcher.
His body count is truly something to behold: most of both Prospit and Derse's populations across both the kid's and troll's sessions, as well as all of the remaining dreamselves of the trolls (thus indirectly killing off at least Feferi, Tavros, Equius, Nepeta, and Eridan for real since they get killed during infighting), all the troll's lands and thus their entire populations, and some salamanders who thought shaving cream would make a good fire retardant. In fact, the only one he cannot actually kill is Jade, though not because of his morals, but because the prototyping of her dog makes him intensely loyal to her...something he hates so much that he demands his subordinates do the deed for him, simply because of his desire to see everything die. This sort of backfires when one of his subordinates does kill Jade. The loyalty he has to Jade causes him to kill the subordinate in retaliation. Then he ensures Jade Comes Back Strong. His actions after that can almost be viewed as a Roaring Rampage of Revenge.
Your mileage will vary with Vriska Serket, intentionally so. On the one hand, she feeds trolls to her Giant Spider, paralyzes and later kills Tavros, Mind Controls Sollux into killing Aradia, blinds Terezi, helps screw up the Kid's Session, and makes Jade think she had narcolepsy. On the other hand, the reason she fed trolls to her Giant Spider is because it would eat her instead, and she was manipulated all her life into becoming who she was. And she feels guilty, to her own surprise.
Eridan Ampora. He was already a Jerkass, but he crosses the line when he kills Feferi and then dooms the troll race to extinction. It is implied, however, that he was subtly manipulated.
While Gamzee would be the last person anyone expects to be this, when he sobers up, monster doesn't even BEGIN to describe him. The worst part? He might just be the only person who could defeat Jack. Subverted, though, since it was revealed that he was under the influence of a lot of things, such as his bloodline, the death of Tavros, and Lil' Cal, which is interesting, considering the entry below. His ancestor, on the other hand, is an unrepentant monster on the level of The Joker.
Doc Scratch is truly something else. He was introduced to the troll universe after the ancestors' original sacrifice solely to transform trollkind from a peaceful race into a hateful and violent one. As the comic demonstrates on numerous occasions, he did a positively bang-up job in that regard. In case that wasn't enough for you, he enslaved and abused a little girl with the intent of grooming her to become Lord English's handmaid, a responsibility she undertook only because, at the end of her service, she would be allowed to finally die. And really, he has a thing about being a creep to little girls in general, from blowing up one girl's eyeball and arm to popping in on their private chats. Thanks to his penchant for deceiving via omission, he fools Rose into creating, instead of destroying, the Green Sun using the Tumor.
And what about Her Imperious Condescension? She committed terrible atrocities, such as massacres against the lowbloods, placed The Sufferer in red-hot irons and had him tortured to death, threatened to wipe out her own people if they didn't obey and listen to her whims, and used The Ψiioniic as a living battery to power her own massive battleship. What a horrible bitch.
Bram from Nosfera made dozens of women into his mind-controled sex slaves and planned to do it to his own wife, the title character
Ditto from Pokeslaughter. A sarcastic, murdering, sociopathic rapist who started all the events in this comic in a failed attempt to take over the world.
Wayward Sons: Doctor Chu is a brilliant scientist who gets most of his results through torturous experiments on live subjects. Or, put another way, he's a professional torturer who learns a lot of useful things while on the job. Either way, he certainly enjoys what he does.
Lulafel from Lumia's Kingdom has the distinction of apparently being born a Complete Monster, torturing animals to death and viciously beating other people as a child and only getting worse as she got older. All this in spite of the fact that she was raised by two loving parents who repeatedly tried to help her. The worst of her atrocities, an event known as the 'Oculus Massacre', has only been hinted at in the comic, and judging from recent comics, it may be far worse than what anyone has guessed at so far.
Professor Wingo from Rumf Adventures, who has no problem commiting genocide on an ancient race For Science!.
The Lanthian priests of Wapsi Square died long before the start of the comic and haven't been shown in much detail, but what has been shown is rather horrific. Their overall goal was to overthrow the existing leadership of Lanthis, and while we haven't seen how justified such a goal was, their methods were so depraved that it doesn't matter what they were fighting against. For starters, they tortured, starved, and raped three young women with the intention of breaking them so completely that they could be made into easily controllable weapons. In the process of capturing said women, they used infants as human shields. Fan opinions of them range from disgust to even more disgust.
Natalie Geln from Khaos Komix is a homophobic, almost nazi-like bitch. She attacks two Transgendered (Charlie, a MTF, and Tom, a FTM) students outside the school, cuts Charlie's hair, taking half of her ear-lobe with it, and orders two boys to rape Tom. She then gives a long speech about how she doesn't want any freaks in "her" school, and they should "Do the world a favour and kill themselves." The worst part? Not even that shit like that happens in real life or that anyone could easily become like her were they to allow certain biases to grow to monstrous proportions. She wins.
There's also Jamie's mother, who may well be even more homophobic than Natalie. Not only does she douse her son in scalding hot water after discovering him Playing Doctor with another boy in an attempt to "clense him", but she cares absolutely nothing about how he feels about anything. As Jamie himself puts it, "she only cares about herself and what she'll get out of something".
There's also The guy who raped Jamie as a child. I doubt anything else even needs to be known about him.
Ed and Dom from Megatokyo. The former is a sadistic psychopath who loves killing people. The latter is a Corrupt Corporate Executive who wants SEGA to own two innocent girls.
Leopold from Scary Gary is definitely this. In the comic, he abuses the vampire Gary and often tries to kill him. He also tortures and murders several of their neighbors and would then often eat them. In a recent strip, he gives a skinny man money for food, and then devours him when he's plump. He also tried to eat his own parents in a Christmas storyline. And in another, he tries to eat a litle baby.
Prescilla/Bonnie in Season 9 of Survivor: Fan Characters is easily the vilest character to ever be drawn in that comic. Just how vile? In their own words:
Prescilla/Bonnie: Regrets? Hell yeah; I wish I could have done so much more. I wish I fucked Lesbocunt before I voted her out. Wish I could have led Adrian on longer before breaking his heart. And that Russian turd...I wanted him pulled from the game, and his leg didn't even get infected; that sucked. And don't even get me started on the Nigger, Beaner, and Chink Alliance.
Barbie: So you wish you did more to hurt?
Prescilla/Bonnie: Yeah. I have a bet with a few of my pals on how many of these cunts commit suicide after seeing this. I just need 3 to do it and I'll win an extra 10 grand.
Emperor Nicholas the Puissant of General Protection Fault, who has conquered the world in an alternate dimension. He kills people who fail him, tortures Nega-Ki to ensure his counterpart's obedience, then threatens to torture prisoners to death in front of him if he wastes time, and it is ultimately revealed that he doesn't want Project Velociraptor so that he can win the war with the aliens laying waste to Earth, but so he can escape and re-establish himself elsewhere.
