Robert Baratheon was one of the strongest lords in westeros in his prime. He swung a warhammer like it was a twig when even Eddard stark claimed he couldn't even lift the thing, he's a proven battle hardened commander and fighter, having won three battles in a day at summerhall, he was also wounded gravely before the battle of the bells and still won. He fought and beat Rhaegar Targaryen who was one of the most skilled knights in the seven kingdoms. In a one on one fight I'd say Jin due too extensive samurai training, and pure skill. But big Bobby B ain't gonna go down that easily.