Something that’s really intense or painful is excruciating. If you go skiing and break your leg in several places, the ride from the slope to the hospital will be excruciating — unless you're unconscious, too.
Excruciating doesn't just hurt. It feels like torture. This adjective actually comes to us from the Latin excruciatus, which means “to afflict, harass, vex, torment.” Extremely painful injuries are certainly excruciating, but sometimes so are tedious tasks or long waits: Watching the old lady in front of you pay for her groceries one nickel at a time can be just as excruciating as 4 broken ribs, especially if you're in a hurry.