Source: Lab Rats #4-6 (2002)
Type: Alternate futureLab Rats, John Byrne's short series about troubled teens drafted by the "Campus" to test unknown tech, wasn't particularly amazing, but it did have some fun ideas working for it. Issues 4-6, for example, has the Rats run a time machine 50 years into the future. As it turns out, breaking the laws of physics creates a universe-wide cataclysm. The Metropolis of 50 years hence is in complete ruin, though it's far from the worse place on Earth. As I will now spoil for you, when disaster hit, Superman was struck with amnesia and found by persons unknown - or to be more obvious than Byrne, by Luthor. And now three generations of Luthors have kept Superman thinking he is the "leader" of a group intent on finding Superman and punishing him for allowing all this to happen. A leather armor with an ugly mask and grains of kryptonite in the seams is really all it takes for the leader to never find out who he really is.
The cycle of unconscious self-loathing is broken when a wizened Jimmy Olsen allies himself with the Rats and shows Superman his original costume. And it's just in time, because aliens angry with Earth for, you know, blowing up time and everything, have just arrived. Superman convinces them to stop destroying our rubble for 12 hours while the Rats return to earlier in their timeline to prevent the launch that destroyed the world... by ramming into the machine with itself before they're ever called in. Timey? Meet Wimey.
And that's another "old Superman" from an alternate future. It could have been its own series.