Came here to say childbirth. Movies usually depict the last couple minutes (the actual birth) as painful but actually it's dilation that's really excruciating, and that can go on for a horribly long time. Mine lasted 24 hours with my first and at one point I almost threw myself out a window, but I feel like I got off easy because my mom was in labor for 70+ hours with me.

The best comparison I can give to people who haven't experienced it is imagine the worst intestinal cramps you've ever experienced, but over your whole torso and 20x the intensity. Or just picture some kind of small clawed animal playing in your guts.

(Inb4 someone says theirs wasn't so bad, lucky you. I had four and they were all as bad, just quicker)