He's nothing if not a loyal hound, he's back at Tywin's feat.
Although Austerlitz is right, the best fighters in GOT are either gone or dead, the absolute best was dead before the series even began, the Sword of the Morning, in Jaime's words ,"I learned from Ser Arthur Dayne, the
Sword of the Morning, who could have slain all five of you (referring to the knights of the King's guard) with his left hand while he was taking a piss with the right."
Although put any of them against the whitewalkers from the books and they're dead meat, unlike in the show the original whitewalkers aren't exactly as lumbering and ugly, they happen to be rather beautiful, dagger swift and extremely nimble. Although they are just as strong as they've been shown to be in the series, rip a man apart with their bare hands.