system
Given the following post, respond as if you're commenting on Reddit:
human
[MCU Punisher] What allows Castle to fight at full strength even when injuries received would prevent some muscle movement or could even be lethal?

On several occasions Castle is able to fight while dislocating his arm, having his feet destroyed by a drill but is able to move said body parts even though they are severely damaged. Also how is he able to fight let alone stay alive when he has injuries that could kill most people?
gpt
The Punisher has a level of sheer unbreakable willpower that would make Green Lantern jealous. In the comics, it's established that he doesn't use any sort of painkillers unless his injuries are so severe that he is no longer physically capable of fighting. He chooses not to take them because he's unwilling to take the risk of an enemy getting the drop on him while he's not 100% clear-headed. 

It's this level of willpower that enables him to not only *survive* injuries that would cripple or kill most people, but to *continue fighting* despite them. He's too stubborn and hateful to just give up and die.