'Game of Thrones' Star -- Slams Steve-O's Frost Giant

Sansa Stark has lots of pent up anger ... and the video of her taking it all out on Steve-O's nuts is pretty damn hard to watch.

Sophie Turner punted the "Jackass" star right between his field goal posts with extremely painful results during an event for a big new movie they're both in called "Barely Lethal."

The flick is about a teenage special ops agent who fakes her own death, then enrolls in high school.