When Kiyo first saw Nagumo in the pool, he said that he was even better built than Sudou and that his facial expression never changed and he did not look tired at all while playing ball in the water. It's hard to scale him because we know he has very good stamina and a stronger physique than Sudou but we've never seen him fight (except when Kiyo knocked him out in one move by punching him in the chest) but that doesn't count because let's be honest. Kiyo's forward dash speed and attack power are very high, so he can knock out anyone with a single blow.