Palutena from Kid Icarus Uprising, especially because the internet loves her and Pit's antics, when I remember most of it was mocking him and gaslighting. I dunno, I like a lot of other bickering duos in games, but she just reminded me too much of grating people in my life. Pit is fine with it, but I somehow doubt asking her to be nicer would help if I was in his position.

In a similiar vein, in Coffin of Andy and Leyley (after overwhelmingly positive reviews baited me into thinking it's deeper than edgy jokes) I wanted Leyley to just die after an hour or few, but the difference is, she's flat out evil, and comically so. Palutena is just the realistic, toxic family member, with the excuse being that gods are assholes I guess.

(I didn't mind Pit and Viridi bickering though, probably because she was an antagonist and Pit/the game doesn't praise her as much)