13Superman Red/Superman Blue (comics storyline)
Ending a larger arc where Superman's powers were already kind of weird (he could be either an electrical being in a containment suit or a normal human), one of his enemies split him into two beings, blue and red, who had the same powers, the same Clark Kent identity, and most
awkwardly, the same marriage to Lois Lane. Blue was reason and Red was emotion, but they were both such jerks that Lois ended up kicking them out of the house until they could reunite somehow, and that was when the super-stalkers of two worlds showed up to fight over both.
What could have been a goofy, charming story (like the short "imaginary story" from which it takes its name) was soured by generic giant monsters and these addled Supermen acting like bad Spock and Kirk role-players, neither one of them considering why Lois might not be cool with becoming a bigamist. It also just went on forever and ever. The gimmick became so oppressive that when it was resolved with no explanation at all, everyone just shrugged and pretended that was fine, rather than invite this nonsense to go on one second longer.