I understand the idea that Superman's energy keeps him young, so I could see Superman looking older after he lost his energy, but he looked like a zombie lol.
Also when did Superman gain the ability to drain energy from nature?
I still don't understand why he looked like a corpse though. I understand the nuclear blast weakening him, but why would it make him look like a corpse?
Yeah but why? I can understand the blast hurting him, but why would he look different? He should have still looked like Superman, he would just be weak.
It was just Frank Miller's interpretation of how Superman looks when he's near death. I don't know how else to explain it. Certainly people in real life have looked pretty close to that from different illnesses, but Superman could actually go further than that and look like a literal corpse because he has the power to regenerate. Doomsday and Wolverine have been reduced to their skeletons and regenerated from it.
I think he absorbed the UV energy the plants absorbed from the sun and that made him regenerate, but not in full health as Batman stated before fighting him. Ideally, he should've just flew outside the earth and absorb sunlight in space, but maybe he was weakened enough and unable to do that. Also made me wonder why he didn't recharge before fighting Batman, that would've maxed out his strength.
Ooooh, I thought these were the results of his radiation. I actually expected him not to be able to go back to living among humans for a while because of it, but it didn't take that long.