While the Light Warriors as a whole are amoral, inept, stupid, violent, destructive and selfish, Black Mage stands out because he wants to destroy the world and everyone in it for no real reason. It's suggested that its his own presence that causes the rest of the Light Warriors to be what they are.
Bob in Bob and George is evil, but still hangs out with his brother George and the rest of the main cast. He even saves George from trouble a few times. However, none of this stops him from occasionally trying to take over the world or kill everyone.
Curse Quest: Avalon is a dead ringer for this. He appears to be inactive and sidelines with the heroes at the moment. However, considering he doesn't give his real name and also using an alias when signing up for the curse quest, it can be assumed he doesn't want to be discovered by the International Guild of Heroes. He cheers on enemies trying to kill his teammates and demands being called Master Avalon.
In Darths & Droids, Pete doesn't exactly play his character evil, but as more of an insane and completely amoral psychopath. Though he doesn't seem to be aware that there is anything unusual about it. And it's R2-D2 of all people. He does admit that he likes the group in this strip, after he GM's a session which turns into a death trap. Lampshaded in #783:
R2-D2: If I was controlling a bad guy, you know what I'd do? Obi-Wan:"If"?
Arudin from Dungeon Crawl Inc is this, though he insists he's "colorfully pragmatic." His most vile deeds occurred years before he joined The Team, when he was an agent of the elven terrorist organization Eldreth Veluuthra. He did a Heel–Face Turn and nowadays he's mainly a snarkyJerkass.
Luke from Freakangels decided one day human morals really weren't his thing and has been going downhill ever since.
Trudy was quite over-the-top evil in the first few years, literally as well as figuratively kicking dogs. As Cerebus Syndrome set in, she became a slightly toned down villain who was manipulating the rest of the cast to take over the world. After being defeated and forced on the run, her ex-boyfriend Trent took over her position, proving to be the most selfish and amoral of the GPF crew during his time there. The fact that both of them were in the same position gets lampshaded.
Nick: Do they make marketing people in a less maniacal flavor?
The trope is downplayed at first with Trent, however. Dwayne shows more patience with his antics than he really deserves, though it's fair to say his feud with Fred isn't entirely one-sided, but Trent does eventually push the Team Dad too far.
Trent:Fired?! On what grounds? Dwayne: Let's see. Harassing a fellow employee. Attempting to murder said fellow employee. Disrupting the workplace with frivolous lawsuits. I don't like you, I'm through defending you to my employees, you just attempted to pull my wife's clothes off... Trent: I think I get the picture...
Baron Wulfenbach seems to keep Bangladesh Dupree on the payroll because it's better to have her using her destructiveness at his call rather than simply running loose. Of course, that leash isn't very tight.
Tarvek considers himself this to Agatha's group, even declaring it out loud at one point.
Tarvek: I'm totally one of the bad guys, okay? I'm a great big devious weasel.
In Gods Playing Poker, Cthulhu himself is generally on the side of hurting people and eating souls, although the actual group doesn't do much literal heroing, being mostly composed of holy figures of various faiths.
The Handbook of Heroes has Fighter as by far the jerkiest member of the protagonist party, committing vile deeds like slaying a good gold dragon for its hoard or killing a magical talking deer for food. An early strip confirms that his in-universe alignment is Evil.
At first, the Trolls seem to have one in Terezi "gallowsCalibrator" Pyrope. In Act Five, however, we meet the other Trolls; compared to Vriska "arachnidsGrip" Serket, Terezi is a saint. The worst thing Terezi has done was leading the protagonist to get himself killed by taking on enemies stronger than he could manage in an alternate timeline, and she did this knowing he would be back. Vriska, on the other hand, forced one of her teammates to jump off a cliff and paralyze himself, then mind controlled another teammate into murdering his lover, and forced Terezi into staring into the sun until she went blind. Terezi haskilled trolls during her time as Vriska's partner in FLARP, but according to her, she only killed the "bad" ones, while Vriska just killed everyone.
There's also Eridan Ampora, who doesn't seem too dangerous initially, merely being a Jerkass with plans to perform genocide on the land dwellers that he doesn't seem too likely to ever actually come through with. Then in Act 5 Act 2, he reveals his plan to join up with Jack Noir, and promptly blinds Sollux and murders Feferi and Kanaya when they attempt to fight him.
And the most unexpected example, Gamzee Makara. Introduced as a dim-witted, good natured stoner who is a devout follower of a religion of clowns and miracles, he seems like a funny character firmly rooted on the good side. Then he runs out of what kept him high and has his religion mocked by Dave and promptly becomes a murderer hellbent on killing all the other trolls in the name of his "mirthful messiahs". While Karkat calms him down before he can kill more than two trolls, he still never goes back to being the good-natured person he was before, becoming a complete Jerkass, and he ends up being a follower of Lord English and doing many things to assist him as well as the only one of the token evil teammates to end up having seemingly no redeeming qualities by the end.
For the Pre-scratch trolls Kurloz was probably the most outright evil, though Meenah and Damara were close behind.
Galatea in The Inexplicable Adventures of Bob! seems to be very slowly growing a set of morals, thanks to her family's influence. She at least acknowledges that hurting innocent people is bad, but she still believes conquering a planet and setting yourself up as dictator is okay as long as no one gets (immediately) hurt. Bob pointed out that people would inevitably get hurt in the long run, and that gave her pause. So, she's gettin' there...
Mike from It's Walky! and Shortpacked!. While not exactly evil, he takes being a Jerkass up to eleven. When he's sober. When he's drunk, he turns into a nice guy.
While the Ragtag Bunch of Misfits in Kill Six Billion Demons are pretty morally grey and plain confused for heroes anyway, Princess stands out among them as a straight-up unreformed Always Chaotic Evil devil, whom Allison accidentally bound to serve herself. Ironically, he's not the one likely to do something that morally shocks the others — he's pretty much just along for the ride, whereas the three real main characters (Allison, Cio and White Chain) are the ones whose personalities and moralities strike sparks against one another.
Richard in Looking for Group. On page two, we see him use an innocent bystander as a human shield. He then gleefully considers the prospect of killing the man's wife and young son, to "complete the set." The rest of the party is grey or good (Cale). Oddly enough, despite Richard killing Cale the first time they met (he got better), and Richard's constant Crossing the Line Twice, by now Cale misses him so much when he is not around that he set his own hands on fire reminiscing. When Richard returned, there were hugs.
Ken in No Need for Bushido is a Sociopathic Herojerkass who is something like a combination of Mugen and Prince Zuko but without either of their noble qualities. He's shown brutally mugging innocent people several times as a way to keep the group in-funds, and his good teammates are willing to tolerate this.
Bezzler the thief in Nodwick essentially stole everything he could get his hands on and nearly bankrupted his party several times before Yeager slipped him a "Magic Helm of C'ntrol-Ault-Delete" (and again until Nodwick dealt with him after this wore off). Although in day-to-day life Yeager seems to play this role despite not being officially evil (often helped by Artax).
DM was also going to enter Kurahadol into the team, but instead illustrated some of the problems inherit to this; he was so excessively rude to his would-be party members that by the end of their first meeting, Luke was asking if they could just kill him off so she'd have to roll up a new character. In addition, the character build was not one that could even work with the party with the key maneuver being a frenzy attack that doesn't distinguish between allies and foes.
Belkar in The Order of the Stick. A Chaotic EvilCard-Carrying VillainJerkass, but Roy is allowed into heaven partially because his influence limited the amount of evil Belkar would otherwise have done. (Exactly how much would that have been? See this comic.) Interestingly, this may be the first non-intuitive trope used without at least a Lampshade Hanging.
Also interesting in that it's played completely straight, bordering on deconstruction. The implications of a mostly good party putting up with the sometimes utterly despicable actions of a teammate who shows them little loyalty are thoroughly explored. And then reconstructed with Roy giving a lecture not only on how Belkar can be controlled, but why it would be a bigger risk not to try. The authorities of Law and Good actually agree with Roy, saying that they believe that Roy's influence has minimized Belkar's evil (and their projections of what Belkar might have become without Roy around are actually kind of scary).
This status quo is gradually changing, with Belkar having undergone a Vision Quest where he's convinced that the only way he can continue getting away with what he does is by pretending to be more heroic and less sociopath. He's still a Jerkass, but considering he's inherited a Morality Pet in the form of Lord Shojo's Right-Hand Cat, he may have begun to genuinely change for the better. But only slightly, since he's still willing to deal with slavers when they don't threaten his cat. Nevertheless, Belkar still is very much "south of Neutral", in Haley's words — which is sometimes not a bug, but a feature.
Bun-bun is a sociopath through and through, but the other characters keep him around partly out of sympathy, partly because his raw toughness comes in handy, and partly because he'd kick their asses for trying to get rid of him. Over the years, the cast has gotten quite good at "Bun-bun-fu", arranging situations so that it's in Bun-bun's best interest to help them.
Riff: I'm going to sweeten the deal! What do you think of this, Bun-bun? Bun-bun:[unimpressed] It's an empty wallet. Riff:[points to bad guy] And I bet his is full of cash and credit cards. And you've got to bodily throw one of us out. Bun-bun: Fair enough! Time to mug and take out the trash!
Even more blatant during the ROKEN arc, where Bun-bun goes up against Oasis under the guise of doing it only for a huge pile of cash, only when he finally encounters her he has this exchange:
Bun-bun: I'll get right to the point, Red. You simply have to stop messing with and killing the dweebs in my life. They suck, I know, but they're my dweebs. You're making me mad.
is absurdly evil. In one arc, it is revealed that his Signature Move, hadoken, is powered by love. That is, he siphons love out of the universe to fuel his power. This has the added effect of raising the divorce rate with each blast.
Chaotic Evil Card-Carrying Villain Jerkass, but Roy is allowed into heaven partially because his influence limited the amount of evil Belkar would otherwise have done. (Exactly how much would that have been? See this comic