I was about to say Ghazkull, but you have a compelling point, considering the beast punched half the Imperium into submission.
I'm sorry but I gotta say Gorgutz, he is just so confoundedly stubborn and knows when to run away, which most orks don't know!
Ghazghkull. The rivalry with Yarrick was one of the first things I read on the wiki. I can respect an Ork that is so into the fight he let's his nemesis live just because of the challenge.