Fulgrim. He killed multiple Primarchs. Most Primarchs didn't kill any other Primarchs during the HH, and he got more than one.
Fulgrim fought and defeated Ferrus Manus, but could not bring himself to kill his brother, however the daemon with the Laeran blade he wielded struck the killing blow. Fulgrim would later fight Roboute Guilliman and only mortally wound him with a slash to the throat with a poisoned blade, and Guilliman would be interred into a stasis chamber. Horus was the only Primarch to have slain another. This info taken from the Lexicanum.
Regardless, Horus is dead, Fulgrim is not, and Fulgrim bested two Primarchs. What did any of the other Chaos Lords do as mighty as that?
The Dominion of Fire. The First War for Armageddon. The Iron Cage. Ahriman's Rubric. Lorgar's actions at Nuceria are what make him the greatest, because he found a way to save his brother, Angron.
You again on chaos threats And all the warlords are ruble to be crushed under my boot. Meaning I have no idea...
Meh, Lorgar is a crybaby. As opposed to winning against another Primarch he got put down and only spared b/c the Raven Guard Primarch was too weak to finish him off. Not one I would put above Fulgrim. To each their own I suppose.
I thought it was more like Corax: YOU BETRAYED THE LAAAAWWWW Lorgar: =( Corax: *Stabs* Any Last words? Lorgar: X( Konrad: Why hello there Corax:=0 Lorgar:=0 Konrad:I'm SpaceBatman Corax: OHHELLNO! *flees* atleast that a rough version of how the Istavaan V encounter went in my mind.
