One of the worst things I have tried to do in an RP, was in a zombie RP, and deemed too traumatizing for a child - who was allowed as a character in an RP with zombies trying to kill her and everyone else. 

What was it? Found a girl who had been affected, but not turned. My character,a gangbanger released from jail during the whole deal, had an idea. It was to have the original girl kill the infected girl, before she went full Zombie. I was told that was too traumatizing for a kid, especially since part included them becoming friends prior to it.