'Game Of Thrones' Star -- Never Had a Chance ... Crushed by Arm Wrestling Legend

The massive "Game of Thrones" star who popped the Viper's eyes out of his head, didn't do so well in the arm wrestling arena, and shockingly went down HARD to champ Devon Larratt.

Yeah, hard to imagine 6'9" 419 pound Thor Bjornsson losing any test of strength, but "The Mountain" met his match in Larratt ... who gives up 200 lbs. to Thor!

2-time champ Larratt joined us on TMZ Hollywood Sports to talk about how he took down Thor ... who, by the way, has been a finalist in the last 4 World's Strongest Man competitions.