You're probably right about losing body parts, I'm sure cancer is more painful though. I've watched someone go through child birth and I've watched someone go through ovarian cancer, I never again want to see anyone have to go through cancer. And we're talking about someone drugged up on phethanol which is basically medical heroin.
Out of the interest of curiosity I actually looked up the most painful thing on the planet and it seems it is actually major burns, apparently it's the worst thing you can endure and still live through.