Your friend reveals that he knows of some weakness that you have, or has a tactic or piece of Applied Phlebotinum in reserve specifically to take you down; you know, "just in case".
Maybe he has been betrayed before, maybe he doesn't trust anyone at all, or maybe he simply thinks you are too dangerous, might someday give in to the temptation to abuse your powers, or most benevolently, Mind [...] [tvtropes.org]