FTs who try to undermine their colleagues, telling the students "their" particular accent, pronunciation and wacky grammar is more correct than the variant spoken by FTs from different countries, and that the students are lucky to have him/her teaching them. I won't go into specifics regarding main offenders here. I won't even identify Larry Orenstein from NY City who is probably still hanging around hairdressing joints trying to assert his flagging virility.
And echoing previous comments, the Zhongwen expert who either corrected other people's Chinese, or laughed outright, despite the fact that his [i.e. Larry's] pronunciation was so RS locals often couldn't understand him. Of course, this was put down to said locals being from backward provinces where they didn't speak the language properly.