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

You've given both of these characters time to gloat about

One-Punch Man - BZPB Wiki

Garou, One-Punch Man Wiki

SSGSS Goku vs serious 100% One Punch Man - Battles - Comic Vine

Saitama, VS Battles Wiki

Why in One Punch Man being too powerful seem to bother Saitama

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

In One Punch Man, which characters know exactly how strong Saitama

Saitama vs Goku: And the winner is… – The Observer

One Punch Man, Best TV Shows Wiki

5 most powerful One-Punch Man characters (and 5 who are weak)

Okay so how many characters now know Saitama's true power? : r

Will the source of Saitama's power ever be revealed? - Quora

20 female One Punch Man characters, ranked by popularity