Black Nate Grey
The God Emperor of Mankind
Thank you.Superman has always been a ridiculous character in terms of power. Power scaling with him is almost nonexistent. That's why arguing who can kill Superman, requires the clarification which Superman, because different versions of him go from kinda powerful to defy all laws of the universe powerful.
We can go from New 52, lifting the weight of earth for multiple days without rest and without sunlight.
to the latest Superman destroying the Forger's multiverse and knocking him out. The Forger is an equal to the Anti-Monitor. Though to be fair, Superman was flying through an unknown number of stars to power himself up.