At the end of a Penny and Aggie storyline, Charisma rants to her illegitimate son's face that he exists to ruin her life, after a series of events he had no control over, in front of her boyfriend. Needless to say, he leaves her soon after.
Aylee (actually her evil clone) gets one of these after she goes through her corporate executive transformation. She attacks the gang's Halloween party and leaves all the guests unconscious outside and taunts Riff with the knowledge that she can kill him and everyone he knows so easily.
Vaarsuvius threatening Elan with death when Elan says that he will not cover up for Vaarsuvius killing Kubota. In addition to suggesting that Elan had an affair with Therkla behind Haley's back. Note that Elan is hir team-mate.
Tarquin. We know his political moves are evil, but in case the audience would feel it justified, he quickly shows that he is still evil. Even Elan realizes this when it's practically spelled out in giant flaming letters made of escaped slaves. Later, Elan sarcastically mentions the trope to him, but...
Tarquin: "There is one more thing, Elan — then you may begin your long walk across the desert, if that's your decision."
Elan: "What, do you have a bunny you need to punch in front of me or something?"
Tarquin: "No, I'm talking about your dismal combat performance back in the pyramid." to his aide "Though make a note of the bunny thing for next time, that's good stuff."
Vaarsuvius is on the receiving end of a kick when Qarr, for no apparent reason, decides that what V needed was to have salt rubbed in the wound of realizing how many people casting Familicide hurt. There was literally no reason for him to do that, especially given how Qarr was there to convince V that it wasn't zir fault and push him/her further into evil, and Qarr kind of ruined that scheme when he was indulging in diabolic mocking.
And there was very little need for Nale to rub it in Malack's face that he had killed his children. He shouldn't have been surprised by Malack's reaction.
He could have chosen a much less mean way to put it, but he does have a fair point: he and Fay are fuck buddies with few-or-no strings attached, so expecting exclusivity is pretty strange. And if she wants something more serious, she could always ASK, rather than trying to browbeat him into it.
Misty Snow from Shadowgirls. She was racist at the age of 5, and when she grew up, she became a teenage Queen of Jerkass. Her biggest feat in kicking a dog? She made Lin betray her best friend Becka for popularity, and led her in a trap, but instead of embarrassing her in public, like Lin thought it would end, Becka almost gets raped by three guys. And Misty was meanwhile playing with Lin's guilt, and thinking about it made Fate Worse Than Death even worse.
And if you think Misty's bad, just wait until she becomes Possessed ByMotherHydra, who surpasses her in kicking a dog like hell. And she has this promo art.
Nemen Yi, the Chosen of Battles in Keychain of Creation. When she first shows up, her moral status is indeterminate: sure, she's trying to sequester the group's precious artifact, but it had just been stolen by the villains for world-ending purposes. Then, after one of the team gets it back, the Chosen of Battles looks like she's ready to throw down on the group — until Marena points out that that would be illegal. Fortunately, the conundrum of whether we're supposed to sympathize with Nemen Yi or not is solved in the very very next strip, as she immediately chooses to try and steal the artifact and bait the rest of the group into attacking her first (so she can "defend" herself) by attempting to behead Secret, on the legal technicality that even though she is a defector from team evil and working for the protagonists, she's still an Abyssal Exalted. Going straight for The Woobie's neck just to get around a bureaucratic roadblock in your path is what we call "a signal".
Cyanide & Happiness uses this, taken as literally as possible, as the entire punchline, and stinger, in one of their animated shorts.
But I'm a Cat Person takes this from the dog's point of view. The kicker's identity is still a mystery, but the aftermath inspires the heroes (at least, one of them) to commit to being on the dog's side.
Seymour, the Knight Templar vampire hunter from Nosfera does this when he kills some monsters after they had ALREADY SURRENDERED.
Although, the one time she fought an actual dog (the Big Bad Jack Noir) she was being heroic.
In the Act 6 Act 3 intermission flash, Cronus acts pretty creepily to Meenah, but his really earns his status as a Jerkass when he goes off on an abusive rant to Mituna for something that very clearly wasn't his fault.
Caliborn takes great glee in doing this whenever he can. It's extremely rare that he so much as interacts with anyone without insulting or physically injuring them in some way, often just for the hell of it.
In Captain SNES: The Game Masta, Mother Brain (a Harmless Villain in the show the comic is based on) takes it half-literally by smacking Captain N's dog Duke into a pit filled with Omega Energy just to spite the Captain. This upsets not only her enemies, but also her henchman, King Hippo.
In Our Little Adventure, Peganone, Eva and Randi were attacked by Angelo. Not only they lost the fight, but Angelo ended up magically forcing the Paladin Eva to slay her own horse. The dramatic effect of this was lessened by her horse easily being able to outrun her, and Angelo getting bored and calling it off. It was still very cruel and unnecessary.
The Comic Irregulars: If you're going to have your bad guy do something despicably evil by destroying something huge, make it something that the PCs care about. Something they've fought for and made sacrifices to save.
Used for an Establishing Character Moment in Terra. In a flashback apparent Big Bad Solus Kalar orders one of his underlings to kill a human civilian in cold blood. When the underling attempts to fake it when Solus' back is turned he isn't fooled and hunts her down himself.
Sandra does this to her entire town once she fully embraces her demon nature. Things get really serious when you realize that she imprisons and tortures(at least, mentally) Sam.
After being turned back (temporarily) into an human again, Sandra steals Mabel's thimble from her, just because she can. However, this time, she takes pity on Mabel and gives it back. This is the first sign of humanity she has showed in months.