system
Given the following post, respond as if you're commenting on Reddit:
human
[DC]Questions on Kryptonians

Unless stated, all questions are about Kryptonians near a yellow star.

Can they feel the same amount of pain as a human from spicy food or does their invulnerability cover that too?

How strong is Doomsday exactly? Superman holds back constantly so that Earth won't become a pile of rubble in space. If Doomsday was an unfeeling, no-control, sadistic creature who could actually pummel Superman to death, why would he not just destroy the planet?

Are humans and Kryptonians related in any way? It seems a bit odd for two species that look exactly alike to appear light years apart.
Edit: crapusername47 pointed out that Doomsday is not mindless. I'd like to clarify.
gpt
* No, spicy food doesn't affect them. They can taste the spicy but it wouldn't hurt.
* Doomsday is pretty much Superman's physical equal. He makes no attempt to hold back and Superman can only fight him if he does not hold back either. He is aware of his surroundings and isn't going to smash a surface he is standing on. Doomsday is not mindless. A mindless animal would not be able to fight Superman so effectively.
* Humans and Kryptonians are not related. Human-like forms are quite common in the DC universe.