The Red Viper was probably the best fighter in the known 7 kingdoms at the time. Can't think of anyone who could have taken him (if he sticks to fighting

).
I like the distinction the show makes between mercanaries like Bronn, Darrio, The Red Viper...brute warriors like The Hound and The Mountain...and battle trained formally trained fighters like Jamie, Jorah, Sir Barristan, the dude with the Flaming Sword..etc.
The Merc group seems to win every time. Even Jon Snow was in trouble with the dude with the knives until that chick stabbed him in the back.
Someone aught to make a Game of Thrones fight game.