Overconfident (3.5e Flaw)
From D&D Wiki
Summary: You believe that nothing is beyond your ability. You can do it all. If you want to take on a Red Dragon solo, you'd believe you'd win. No doubts. Seriously.
Effect: If the character is ever challenged to an act or to battle, the character must make a Will save (DC 15 + character level) to back down.
If the character fails the challenge, they lose -2 on all rolls and checks due to personal embarrassment. This penalty is cumulative and will last until they successfully defeat whatever they were challenged by that caused the penalty. These penalties are negated during a challenge.
Benefit: Bonus Feat