system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Why did it seem like Vader was so badly injured and in pain after Luke knocked him off his feet and cut off his hand? All he lost was a prosthetic limb.

If Luke was using some unseen force power that blew his ass apart, then I can sorta understand why he got so wrecked in that scene.
gpt
Vader is, essentially, a full body burn victim who does not take pain meds in order to strengthen his connection to the Force. Basically, Luke defeating him made his focus drift and he finally allowed himself to feel the pain.