Potentially most surprising..
I want to know who you think as a character has the most potential to surprise the villain/hero/reader.
This could potentially fall under most underrated, as some heroes/villains always seem to be written so poorly.
For example:
Aquaman - not written nearly as powerfully as he should be... anyone who moves freely at crush depths is way stronger than he is usually written.
Rhino - With his size, strength, and speed,.. he should be beating down teams instead of falling victim to his own self. (Yes I realize he's doing better now, but I'm not convinced it will last)
Plastic Man - Turn him loose already.