The connecting record
shownThe End and the Death: Volume III · 2024
The Emperor of Mankind killed Horus Ascendant in The End and the Death: Volume III.
and unmade his soul entirely, so that nothing could bring him back
What each of them is ranked on
The killer · The Emperor of Mankind · rank 1
Ranked before the Throne — heresy
He made twenty demigods to specification, held a psychic beacon open across a galaxy so ships could navigate at all, and beat Horus at the moment Horus had everything four gods could give him. The Throne is the asterisk and not the rank: for ten thousand years he has been a dying body maintained by machinery, and the Imperium's entire theology is an argument about what the man on it used to be able to do.
shownThe Master of Mankind (RU ed.) · ch. 2, and the cost in ch. 19 and ch. 24
He cannot rise from the Golden Throne without the paths between the Imperial Dungeon and the webway collapsing, and the Throne is fed with the lives of a thousand psykers to hold them open. — 2016
statedHorus Rising (RU ed.) · preamble
Established as the creator of the Primarchs and the architect of the Great Crusade. — 2006
statedA Thousand Sons (RU ed.) · ch. 22
Made the primarchs with technology recovered during the long wars and the help of geneticists defecting from the Martian Hegemony, as generals for the army he intended to raise. — 2010
The victim · Horus Ascendant · rank 2
Everything four gods could fit in one body — heresy
All four powers backed him at once, and briefly he was the strongest thing in the galaxy on that basis. He was not the first — Be'lakor, far below him here, holds that — but he is the one they chose after giving up on a champion they could not steer, and the difference between the two entries is what the gods learned in between. He killed Sanguinius, broke through the Emperor's guard aboard the Vengeful Spirit, and left the Emperor in the state the Imperium has been managing ever since. Second because it did not hold: the same duel ended with his soul annihilated rather than merely his body.
shownFalse Gods (RU ed.) · ch. 17
Turned on Davin in the temple of the Serpent Lodge, and given power by the gods of the warp. — 2006
shownThe End and the Death: Volume II · 2023
Kills Sanguinius aboard the Vengeful Spirit and mortally wounds the Emperor.
shownThe End and the Death: Volume III · 2024
Destroyed utterly by the Emperor, soul included, so that nothing can return.
What this does not settle
One death in one work. It is the only place the record puts these two in the same room, and it is evidence about that meeting and nothing wider — not a general matchup, not a rematch, and not a ranking of its own.
The ladder above it is argued from everything either of them has been shown doing; this page is argued from one citation.
Where the two disagree, the disagreement is the point, and it stays visible rather than being resolved by whichever of them happens to be on this page.