Penelope getting lobotomized and all of a sudden betraying Bentley for MONEY, when Sly left them MILLIONS of dollars, and being the twist villain once again.
Sly ruining the life with Carmelita he's spent three goddamn games trying to get, the woman he loved so much he faked having amnesia, stopped talking to his lifelong friends, and gave up his family's vault, with all their history, and uncountable amounts money and gems for. To do "one more heist." when every time Sly's stolen it's been to further goals. To fight the Fiendish Five, to get back pages of the Thievius Racconus, to stop Clockwerk, finding his families vault. Sly wouldn't give his life away with Carmelita just because he wants to do another goddamn heist, fuck off.
Carmelita genuinely got shit done. She was no nonsense, fiery, confident and held her own. Funny how she's actually a well written character, one that all the shit modern writers try to make now and fail at. Sly 4 then takes her, somehow makes her look like anything but a fox and instead has her look and act like a whore. She thirsts after Sly's ancestors and they make her a goddamn belly dancer, outfit and all. Why, because she's hot? Go fuck yourself.
Murray, my favorite character by a mile who is no longer THE Murray and instead goes right back to who he was in Sly 1 being the dumb, fat, comedic relief getaway driver. Giving up ALL of his wonderful character development in 2 and 3, that made him more than just a "fat pathetic weakling." He was a fear stricken and controlled dumb getaway driver in the first game. By the end of the series he's a protective, confident and loyal friend who finds his resolve in his strength. all of that is thrown away, to get him scarfing down cheeseburgers and humiliating himself in a geisha outfit, like Carmelita humiliated herself by being a belly dancer, cause why the fuck not. Fan-fucking-tastic.