I think I'm going to knock my friend out with a frag grenade in PUBG mobile.
Do you think that's suitable for this situation?
He has been telling me he'd beat me to a pulp if I ever caught him out in public, so I figured this would be appropriate
It is hard not to make things difficult in a game for somebody who wants to mess with you in real life but games are meant to have fun. If he dies in the game, the game will end.
I don't care. In this case, I killed him.
It sounds like you and your friend are both being jerks to each other, so it may be a good idea to sit down and have a talk with him. If you both keep being rude to one another, you're going to ruin your friendship.