That would only reverse time for him… Which to the people in the frame of reference of the comic, is irrelevant. The only change to them would be the absence of Superman.

So many worlds vs singular timeline is still the question. With relativity suggesting many worlds, and the twin paradox, suggesting a convergent timeline.

…both can’t be true, so it’s more likely you can’t go faster than light and have mass. You would probably just get so fat you blot out and reset the universe. Which is why it’s probably important we never try going at the speed of light…

Not that it matters, because destroying the universe would be the SUCCESSFUL outcome. Spaghettification of the equipment/personnel would be the fail state.

One possible outcome of the comic would be a spray of chains of atoms and subatomic particles that used to be Superman, spewing forth at near light speed as it cuts through building, people, and landmass topology (mountain and stuff). A super sonic laser of what used to be Suoerman.

…and that’s the fail state. The success would be Superman replaces everything everywhere… Possibly then condensing backdown to a pinpoint explosion of pure energy on deceleration.