Theres only one thing I wont tolerate to any degree at my table, and that's genuine malice-fueled PVP. I will not allow anybody to use the game I am running for them in my house, out of my own pocket, to settle a personal vendetta against another player. If two people genuinely don't like each other, and they cant even be civil to each other in the same room, one or both of them are leaving. I don't care if somebody finds bullying somebody to be fun, if both players aren't in on the planning of the character conflict, and if theres an intent to hurt somebody in real life in some way, youre gone. Its my one line that I absolutely will not cross under any circumstances, and one of the few things I suspect a majority of people would agree qualifies as objectively badwrongfun.