It seems that it is not only about going back in time.
Today with the One Punch Man manga it is being seen that Saitama is even reaching the level of a God, leading him to rise even more as one of the most powerful characters in anime and manga and of popular culture in general, since there are very few fictional characters that could match its power, with some of the most notorious names being Goku and Superman. And even with these names, everyone will continue betting on Saitama.
Under this same premise, Garou has put Saitana in check, this being the only character capable of matching him within One Punch Man, although it should be noted that his destiny is in suspense. Be that as it may, it seems that the bald hero has exceeded his limits with the creation of Zero Punch in chapter 166, leading to this gaining enough strength to defeat what is today his biggest rival.
Saitama would have surpassed the power of time itself
It should be noted that the power level of both characters is so great that they took the fight to a moon of jupiter so as not to destroy the Earth in the process, allowing Saitama to fight without worrying about others and ending up not only defeating him, but also obtained part of his powers and could go back in time to save Tareo.
In this way, although Zero Punch may seem to have been derived from Garou, the truth is that this only allows him to travel back in time. Nevertheless, create a paradox by avoiding the death of Tareo, this being a phenomenon known as causality reversalliterally managing to make the impossible possible, as Saitama manages to erase his present and pass into his past body as if nothing had happened.
For the rest, it should be noted that it is not known how this ability will be used in future arcs, since Saitama has reached a level that makes him invincible, which could cause him to end up getting bored with everything around him over time. We will have to be attentive to what is to come in One Punch Man.