Superman. This would be my pitch:
Superman's whole thing is his nigh invulnerability. It's a pretty core characteristic, and changing it would make you feel less like Superman.
And it could be an interesting dynamic to play with. As Zod says in Superman 2 his weakness is "he cares - he actually cares for these people". That's what hurts him, and you could play off of that in a game.
I can imagine a Superman game where every civilian is your 'health bar'. Where them becoming injured puts your 'health' in jeopardy, and their death removes 'health'. Where you're balancing fighting threats with removing civilians from danger. Fighting foes with fighting fires. Where you grab an enemy and take them to an unpopulated area to really let loose with your powers. Being hit isn't about the damage you take, but the building you crash into. Having debris hurled at you isn't about how hard it hits, but the civilians around you.
Boss battles would basically be You vs. The Hulk from Hulk: Ultimate Destruction, be it Lobo, or Metallo, or a huge Toy-Man mech.
I can imagine that game. Flying up, looking down with 'Action Vision', and deciding how you're going to manage the threats of a city. Essentially the mechanic of rescuing survivors in Dead Rising, extended to a dynamic Metropolis. How you'll deal with the supervillain down there on the left, and the helicopter in peril on the right. You could really lean into what makes Superman unique.