^ Zabuza say himself that Haku have to much pity for his ennemies, and also i'll just invite you to check info from his wiki page, i'm not coming up withsomething and i kbow the personality of the character >.> check his personality info that's all
Haku on 4's War was stronger, bc of his erased personality, but he wasnt able to beat Kimimaro. Boner on 2nd stage will break mirrors and all ice anyway, wont receive any damage and oneshot Haku with drill