I had a mentor horror story that was the mentor tank being #2 to the point of over compensating. They straight up refused to participate in the morbol guildhest unless we completed it in exactly the way they lectured us to do it, but tried to make it seem like they were the one being altruistic and good-deed-doing. They said such gems as, "See how that didn't go well. Let's work together this time!" and "I'm sorry you're feeling angry, but everyone will be happy and we can get this done faster than just running in by doing it the way I say." after they literally stood there doing nothing when the bard ran in and pulled before they finished their long lecture on how to complete it the way they wanted to. They wasted so much of everybody's time with the wipe and ensuing 'discussion' and actually had the nerve to blame everyone else for it. Oh yeah, and nobody was a sprout. They were literally there just to lecture people about how to complete content, and force them to fail it if they didn't follow instructions.
I've never blacklisted a person so fast before or since.