Well this is my thoughts-
My top three Primarch fighters would have to be-
Angron (Is a freaking monster! Carries twin Chainaxes and had a entire mountain fall on him (Badass
LEJ (Beat Russ in a duel though only due to his speed, a brilliant Tactician Horus mentions in one of the HH Novels that LEJ has the second highest ammount of victories bar the Warmaster himself)
Russ (Again Russ is a monster in battle, getting in the thick of it he is amongst the stronger of the Primarchs)
Nyctophobia- Fear of the Dark Angel.
"No one ever spoke about of those two absent brothers. Their separate tragedies had seemed like aberrations. Had they, in fact, been warnings that no one had heeded?"
'Killing a man is like fucking, boy, only instead of giving life you take it. You experience the ecstasy of penetration as your warhead enters the enemy's belly and the shaft follows. You see the whites of his eyes roll inside the sockets of his helmet. You feel his knees give way beneath him and the weight of his faltering flesh draw down the point of your spear. Are you picturing this?'
'Is your dick hard yet?'
''What? You've got your spear in a man's guts and your dog isn't stiff? What are you, a woman?'