system
Given the following post, respond as if you're commenting on Reddit:
human
[DC Comics] Superman is supposed to fight a major battle - but is incapacitated. He's taking on an opponent who's equally as strong but twice his size. Who would replace Superman?

This is *not* about who would win, this is about who Superman would get as his replacement if he was too incapacitated to fight in a battle. As for the opponent, assume it's a one-off, but powerful villain who's equal to Superman in terms of power but a human alien twice their size - and a character not in any current DC Comics continuity.
gpt
If he's trying to hide being incapacitated, which makes sense because his reputation is a deterrent, probably the Martian Manhunter. He's roughly as strong and a shapeshifter. He's impersonated Superman before to maintain the illusion that Clark Kent is not Superman.