I would bet all the money I have now — or ever will have — that he would beat you, badly, in any form of singles combat. (sbnation.com)
But, it's not just singles combat like in the show. (dualpixels.com)
The Sand Snakes — the three bastard daughters of Oberyn Martell — sought vengeance against the Lannisters for the death of their father, killed while showboating in single combat against the Mountain (serves him right, got ta play to the whistle). (sbnation.com)