Saitama's limits are unknown. How strong he is, how tough he is, how fast he is, all of it unknown. There is no way of knowing if a certain entity can beat him or not unless we see Saitama do a feat that surpasses their limits. Anyone saying Superman can beat Saitama is blowing smoke out their ass and are probably a Superman fanboy who knows nothing about Saitama. There is no way of knowing how this battle will turn out, which is why I hate this fucking argument.

Why is everyone turning Superman into a murderer? Even in Man of Steel, him taking a life was a big deal (and casualties were a big deal in Batman vs Superman).