Do you have any horror stories about problem players or DMs being unfair?

I’m playing a DND homebrew game where we’re all villains. Sneaking around and stealing stuff, no qualms about killing innocent civilians, etc. Except there’s one player who is borderline refusing to work with the party, including attacking other players for no reason. I get that we’re playing evil characters, but surely the least you could do is work together with your fellow PCs. Evil doesn’t mean “I hate everybody”, right? It’s a frustrating experience, and I just feel bad for our DM who is new to DMing and doesn’t want to disappoint their friends.