Don't trust him, he's a turncoat who always changes his stance depending on the situation.

turncoat 是由 turn（转变）和 coat（外套）组成的复合词。字面意思是"翻转外套"，比喻那些改变立场或背叛原阵营的人，类似于中文的"墙头草"或"叛徒"。