Crayons
Iconoclast
I cannot stand it when a character is boring and has no motivation to be in the story. I'd much rather play with dark edgelords and Mary Sues than with someone without a personality.
Ah, the anti-Sue. A Sue trying so hard not to be a Sue that it revolves all the way around and becomes one.
On a related note: I can't stand characters who are pathetic. They can't do anything on their own, they spend all their time getting other characters to do stuff for them, they crumble under the slightest bit of tension and also, everyone's favourite trait lol, act shy and awkward. These kind of pity-seeking characters just invoke the red mist in me, I hate them so much it makes me legit angry.
Also here's a pet peeve: characters that never change and develop despite their experiences. It defeats the whole point of them being a character imo. Just replace them with a cardboard cut out, or a vase.