Due to his great power and being virtually indestructible, Saitama is an indifferent person. Even the mightiest foes pose no challenge to him, so he does not take his hero work seriously, goes through everything with little to no effort, and yearns for an opponent that can provide him with a challenge. Saitama tends to come off as abrasive to others and often is inconsiderate of their feelings or how his words affect them. That isn't to say he is intentionally malicious or rude.