I got a character out of a convoluted plot by having her get injured and sick, and when this writer revealed to me she wanted my character to become impregnated with some apocalyptic child, I said no way in heck and put my character at death's door. Besides, that RP was already so full of pregnancies and multiple births anyway it was really getting annoying. If someone wants their own character to get pregnant, that's their decision, but they should definitely not try to scheme/trap someone else's character into it without the other writer being fully on board with it.
Then there was this other writer who could come up with the most twisted ideas. I'd just get through with one exhausting situation, and she'd come up with another that was just as hellish and cringy. She had two different women, on two different occasions, begging to get beat up because they thought it would make the world a better place somehow - and all because they were riddled with guilt and fear thanks to some sadistic creep she just loved and couldn't get enough of. Even when she and I tried ring on different lists, that I ran, which had much lighter settings, she still found a way to ram this creep in by the back door. through some character's nightmares, which one of my characters would always have to suffer through hearing about. When I managed to separate those characters, she rped on another list with me and tried to manipulate things in order to bring him back via inverted parallel universe deal where he was supposed to be a good guy now, and one of my characters, who had been his sworn enemy, was supposed to save him.
She did too many other things as well, and one of those was writing every evil character with a ton of attitude, and every character who was decent, had absolutely no guts and/or no power. And when her characters supposedly turned from bad to good, she also went from tough talking, swaggering "Nobody's the boss of me!" to a sickeningly simpering spineless wuss.
On another list I ran, there was this extreme Mary Sue, and it was hard to tell writer and character apart. She got on the list and posted a horrific fan fiction where everybody in the series the list was about, was godmoded into catering to her character's every whim and wild, irrational mood swings. And her character trash-talked, misbehaved, treated everyone like crap while feeling terribly sorry for herself. And get this. she was blind, but could tell when someone looked at her dress. She hauled some boy out on a dance floor, too. In an unfamiliar setting I might add. And wow did her writer ever blow a thousand gaskets when I told her that her "blind" character was not realistic, nor was she going to get away with acting like that. She made ridiculous excuses, told me that allowances should be made for the "poor little blind orphan" and then she resorted to personal attacks. I kicked her off the list and shut it down since people were more interested in shipping on other lists. Bleckh.
On another list, a writer tried to make her characters the centre of the whole setting. So much that the main canon character's life would end if her original character's did. It was all really convoluted. And she threw some kink into things too. She also tried to get a romance going between one of my characters and one of hers (a human version of a canon character that was actually an ape). I wasn't into it. She also had a thing for bad boys. And British accents/dialects. Gosh, that got annoying. Ape Boy was assigned a Cockney accent. I tried extracting my character out of her character's story by bringing in a new doctor for my character, who had gotten sick. But she just included him in her plot, gave him an especially stuffy manner of British speak that didn't suit him, I mean, he was almost sounding like someone perpetually reciting Shakespeare.
So, there have been some things that were really cringy, and a bunch of other stuff that just piled up until I'd had it and called it quits with the various people involved.