Mountain 2/2 – The Mountain has entered many melees and jousts but didn’t win any. Most of what we’ve heard about him are war crimes but his battles aren’t much better. He’s lived but was rebuffed unless he has the numbers. Cercei named him her champion but she values brute force and The Mountain would be terrifying to sell-swords that Cercei would assume Tyrion could only get to champion him. His reputation is really made on his war crimes. He’s a bully and I think most in the books see that.
Here’s what Jaime thinks of the Mountain:
“The realization chilled him. Robert had been stronger than him, to be sure. The White Bull Gerold Hightower as well, in his heyday, and Ser Arthur Dayne. Amongst the living, Greatjon Umber was stronger, Strongboar of Crakehall most likely, both Cleganes for a certainty. The Mountain’s strength was like nothing human. It did not matter. With speed and skill, Jaime could beat them all.”
I wouldn’t say that he dismisses the Mountain, simply that he thinks that his speed and skill can compensate for his inhuman strength. And at the end of the day, Gregor is on a short list of who the best swordsman in the kingdom thinks could compete with him.
As for his skills, I don’t think he’s the most skilled jouster ever, but he is good enough to get into the semi-finals of a major tourney. That’s not nothing, but clearly his skills are more in the direction of the melee, and we’ve seen how brutally effective he can be on the battlefield at the Green Fork, where he turns what is supposed to be an engineered route into a victory.
He’s not invincible, but he’s definitely among the most dangerous men in Westeros.