Dilbert. The character Alice has a short, violent temper and often punches men with her "Fist of Death". This is always Played for Laughs. Then again, the comic plays everything for laughs. At least Alice is treated as the violent nutcase that she is.
One comic had Dogbert beating up people in line for a movie. As the author pointed out, this is funny for the same reason: dogs are thought of as weaker than humans, especially if they try to fight human-style, so a dog punching people's lights out is funny. Even if it's Dogbert.
Peanuts could be considered a case of this. Lucy is always throwing her weight around and slugging the other kids (not just Charlie Brown - probably her most frequent target is her own little brother Linus), but the comic never really makes it seem like she's in the right or sympathetic - often calling her a "fussbudget". The other kids never really call Lucy out on this or try to stand up to her though, and she rarely gets in trouble. Although in the case of the kids standing up to her, they might just not want to get on her bad side, and as for her getting in trouble, There Are No Adults.
Charles Schulz also went on record in several interviews as saying that while a boy bullying a girl wouldn't be seen as funny, the gender reversal in a girl bullying a boy would be seen as funny.
Lucy is the most obvious case but all of the girls have some level of violent streak. Even Marcie is surprisingly eager to slug people in some strips. Linus' blanket whip is as far as it goes for the boys and that only gets used against people off-screen.
One running gag in Snoopy's stories was to have a man say a bad pun or something stupid. The woman would then hit him with any manner of objects.
In Bringing Up Father, the title character, Jiggs, would often have various kitchenware thrown at him by his wife. An early MAD parody from The Fifties deconstructed this by having an Art Shift on every other page where Jiggs is suddenly drawn realistically, and is covered in blood and scars, and has missing teeth due to his wife's beatings.
Played for laughs in one strip ofLuann, where apparently the classic sawing-a-girl-in-half trick is seen as violence against women. When Bernice suggests sawing Gunther in half, the counselor doesn't see a problem with it.
Averted in Calvin and Hobbes, where Calvin and Susie beat each other up in roughly equal amounts and are both portrayed as just typical vendetta-driven kids being kids.
Played with even, Word of God indicates that this is their way of likingeach other. Calvin acts obnoxiously, which repels Susie, which encourages Calvin to act even more obnoxiously.
FoxTrot: Paige often gets away with beating up her little brother Jason. There are times where she gets punished for it, but it's still hard to imagine a 14-year-old boy beating up a 10-year-old girl being Played for Laughs in the same way.
In a 2006 strip of◊ Garfield, Jon attempts to hit on a woman. The woman, apparently unprompted, responds with a long spiel - half the panel - detailing the (cartoonish) physical abuse she's about to inflict on him. Either Jon is just that repulsive to anyone not named Liz, or it's this trope in action. Mitigated somewhat since Jon takes it in stride, it sets up the punchline, and it's left ambiguous as to whether she actually followed through on it or not.