Characters aware of Saitama's power, One-Punch Man Wiki

Despite being the most powerful being in the series, Saitama's power is mostly unacknowledged, especially before registering as a professional hero for the Hero Association, due to him not claiming his achievements. However, few characters are aware of it by sensing Saitama's potential or witnessing his abilities first-hand. Even so, some still reserve doubt about his true power, whether because of their pride, prejudice, or skepticism towards his comparatively low hero rank and simple training

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