In the Percy Jackson movie, it doesn't really show it. It never states it in the series until the last novel but you can clearly see through the whole series that his fatal flaw is loyalty. He would...
OK i know a few, but their of the demigods, not the gods, but i guess they could be the same. anyways...- Nico and Bianca's (Hades) flaw is that they hold grudges, like for a long time.- Percy's...