Superman, the one who fell - Phillip Kennedy Johnson

In "The Golden Age" Jonathan Kent is back from the 31st century and fighting cosmic threats alongside his legendary father, Clark Kent. But when an interdimensional breach opens near Earth, Jon recognises the creatures that emerge: the cosmic leviathans that the Legion of Super-Heroes credits with the death of Superman! As Superboy desperately tries to save Superman's life from the leviathans of the breach, Superman discovers the breach's shocking origins. But with his powers mysteriously fading, he is utterly outmatched. Can Superboy change the course of history and save his father's life? Collects Action Comics #1029 and Superman #29-32.