>>96150683 (OP)Not having their character behave as they should.
I know /tg/ gets bottom blasted when a player has their character do something retarded or dickish and say "It's what my character would do." However, I am of the opinion that is a very valid response. What is bad form is when the player doesn't expect fallout for that action.
As an example, I was playing a legitimate kleptomaniac in a game, so I was stealing shit constantly. Useless shit most of the time that nobody would give a fuck about like flowers in a vase on a shelf. Any time we changed scenes, venues, etc, the first thing I did was swipe something.
All well and good until you steal from a dragon's hoard with the dragon right the fuck there. Got caught. Said "I got a condition. I steal constantly. These other guys have no idea I am doing it. Don't hold them responsible." and was absolutely cool with getting roasted right on the spot and rolling a new character. The annoying players would demand they get away with their bullshit, expect the party to back them in up in a suicide move, and other unacceptable bullshit. Stinkfinger Steve stole the panties of a cloud giant once, getting blasted for trying to steal a fucking skull sized ruby while the dragon was looking directly at him was an appropriate death.