Most of my characters have some quirk or character trait that could be considered exploitable though it's incredibly rare I find that anyone ever tries. That's probably just down to people not really bothering to explore other people's characters that well, or not taking note of subtle clues in combat that display the character's weaknesses. 

The most obvious one is probably Fury, his character flaws are pretty close to his only real weakness and your best chance of beating him. I think people often underestimate how interesting a character that can exploit backstory or emotions would be, I've only tried to develop a character of that kind once and I never got to explore his usefulness fully.