Well, first off, he was easily one of the best warriors of the original legions, to the point that he was almost Primarch-like. Secondly, he was specifically geared out to fight the most powerful chosen warriors of Chaos, and as such was loaded out with the best anti-Chaos gear the Imperium could find at that stage. He wore artificer armour, not terminator armour, and used the original Black Sword, a massive two-handed blade which he was strong enough to use one-handed. He was the embodiment of the horouable warrior ethos and the knightly codes, but raged against the fallen Marines with incredible fury.
Basically, you're looking for something halfway between a High Marshal and Rogal Dorn.