So that guy can lift heavy objects, fly, move at super speed, see through things, and shoot fire out of his eyes? Damn, it's a good thing that he's a Superhero because he would make one hell of a villain. Basically, this trope is when a character expresses the sentiment that it's a good thing that so-and-so is on their side, because they would make a dangerously formidable enemy. Sometimes this is followed up with the joke "at least I think s/he is" or a variant thereof. Or a less certain "...he is, right?" This is also likely to be said by someone who works with a Heroic Sociopath.