Although I found Curze in UE rather over the top,
based upon betrayer and the fight Russ vs Angron, I would say Angron definitely has an edge,
The Khan was convincing against Mortarion, I think he won on points,
Fulgrim got help from a Daemonic sword...
but these are rather pointless discussions as in the end Kharn the naysayer is right, Rupert would have beaten them all, if he was not suffering from cmd
we have heard about the martial prowess of Sanguinus and his wrath, it's about time we actually get to read about it