I can believe that. Before O'Neil finally established himself as one of the perfect writers for Batman, he messed around with Superman and Wonder Woman in some bizarre ways. He de-powered Wonder Woman, turning her into a martial arts expert who (if memory serves) ran a flower shop. He tried to tone Superman down by cutting his power in half, which didn't really do any good since infinity divided by two is still infinity.
But all the same, he did do some very worthwhile stuff with Superman and other truly powerful Justice Leaguers. In World's Finest 198 & 199 (November & December 1970), strange creatures called Anarchronids are zipping across the universe at several times light speed, which is causing the universe to unravel.
The Guardians of the Universe recruit Superman and Flash, the two fastest beings in existence, to run just as fast in the opposite direction to cancel out this effect. They give Flash a medallion that will provide life support and form a roadway in front of him as he runs.
Aside from the apparently minor issue of saving all of Creation, Superman and Flash also look at this as an opportunity to finally find out which of them is faster. They had raced twice before, once for charity and once when forced to do so by alien gamblers. Neither of those events produced a clear winner. Now they would know for sure.
So they take off, running head-to-head across light years. They are attacked by the Anarchronids, run into
trouble with an exploding star and briefly get stuck in a pocket dimension, but they overcome all this and keep going.
In the meantime, the whole universe-unraveling thing has thrown a pajama-clad Jimmy Olsen back through time, giving him some adventurous moments both in ancient
Eventually, Superman and Flash discover the Anarchronids were created by General Zod and some other Phantom Zone criminals, who will use the destruction of the Universe to create a portal that will allow them to escape from the Zone. In the end, Superman and Flash, both paralyzed from the hips down, crawl together towards the switch that will destroy the Anarchronids before the Universe falls apart. Which of them will reach the switch first?
It's a really fun story, casually throwing out one cosmic-level idea after another. It never gives in to its basic silliness or otherwise places tongue-in-cheek. Instead, it takes itself seriously--as most comic book stories of this sort should. It doesn't try to come up with faux scientific explanations for all the wild events taking place--it simply creates a world where such events are possible; a world where "run really fast in the opposite direction of the Anarchronids" is a reasonable thing to do. Because of this (and because of Dick Dillon's solid art), it produces a nice amount of honest drama. It was a good balance of characterization and fantasy storytelling that fit just fine into a superhero universe.