Incompetent (3.5e Flaw)
From D&D Wiki
This person can't be trusted to do any thing, save sabotaging the enemy. This character can never get it right. If they ordered soup, he gives them salad.
Effect: You cannot provide a flanking bonus for friendly creatures or take an aid another action. You never gain bonuses to skill checks from skill synergies. Additionally you half any competence bonuses granted to you.