system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU] what makes thanos so resistant to damage?

It takes iron man with his bleeding edge armour just to make a cut on his body, but Thor with stormbreaker can injure him like a normal axe would to an average man. Stormbreaker is said to be able to kill thanos, but what about thanos makes him so hard to kill, and what about the axe means that it is able to kill thanos where other weapons would fail? If it’s the infinity gauntlet, does that mean that iron man would have done more damage to him if thanos hadn’t been using the gauntlet?
gpt
Thanos doesn't have an "origin" for his strength described in the MCU (yet), but in the comics he's a Deviant Eternal - basically a superpowered mutant, from a race (the Eternals) created by the Celestials that were already on a par with Thor. 

And it's implied (or maybe stated IDK) that he further enhanced himself with technology later on his quest for power.

So basically, imagine if Thor had a permanent Hulk-style mutation on top of his already massive durability and strength, and then he went around finding and drinking Super-Soldier Serum and Heart-Shaped Herb to become even stronger.