Personality wise, probably his recklessness. He’s always gotten away “fine”, so he never learns. He doesn’t ever watch out for himself, and is always ready to battle, regardless of his injuries. Even on the verge of death, he won’t stop until it kills him.
If not that, his petty nature. He’ll never admit he was wrong, and sometimes he’s a bit too blunt. Very dense, far too stubborn. He doesn’t have good control of his youkai, though, and that combined with his recklessness is a recipe for disaster. He’s endlessly flawed and rough around the edges, but I love him all the same.
Strengths. Due to having half youkai blood, his strength is better than average, he has superhuman speed, and quicker healing, to name a few. He’s good at surviving on his own, and doesn’t take shit from others. Due to necessity. He’s also quite spirited, and that gets him through a lot.
He takes everything to the extreme, and glosses over the bigger picture, essentially.