The connecting record
shownOverlord: The Dwarven Crafter
Ainz Ooal Gown killed Olasird'arc Haylilyal in Overlord: The Dwarven Crafter.
one [Grasp Heart], in the dragon's own throne room
What each of them is ranked on
The killer · Ainz Ooal Gown · rank 1
Momonga — the Sorcerer King
Killed Shalltear Bloodfallen, a level-100 built as a counter to everything he does, by planning the fight before it began: a super-tier opener, a bluff about mines laid in the air, and a guildmate's white armour worn through [Perfect Warrior] once her mana ran low — dropped at the end for the super-tier spell that killed her. Nothing else he fights is numbered near him. A Frost Dragon Lord dies to a single [Grasp Heart]; the Elf King, his mana gone against walls of skeletons, runs once Ainz has destroyed his Behemot; and at Katze Plains one super-tier spell kills seventy thousand men in seconds before the five Dark Young it calls up start on the rest.
shownOverlord: The Bloody Valkyrie · vol. 3, ch. 4
Opens the fight against Shalltear with the super-tier spell [Fallen Down].
shownOverlord: The Bloody Valkyrie · vol. 3, ch. 5
Fights the last stretch in Touch Me's armour, wearable through [Perfect Warrior].
shownOverlord: The Bloody Valkyrie · vol. 3, ch. 5
Casts off [Perfect Warrior] and kills Shalltear with the super-tier spell [Fallen Down].
All 8 citations
statedOverlord: The Bloody Valkyrie · vol. 3, ch. 5
Reckons himself, as a level-100 magic caster, about the equal of a level-33 warrior; [Perfect Warrior] makes him a level-100 warrior whose stats far outstrip Shalltear's, since she is not a pure warrior.
shownOverlord (anime) · S01E13
Appears in Touch Me's silver armour and cuts Shalltear across the chest.
shownOverlord: The Dwarven Crafter · vol. 11, ch. 5
Kills the Frost Dragon Lord Olasird'arc Haylilyal with one [Grasp Heart].
shownOverlord: The Caster of Destruction · vol. 9, ch. 4
Casts Iä Shub-Niggurath on the Royal Army's left wing and sets five Dark Young on the rest.
shownOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Lowers his walls of skeletons and destroys the Elf King's Behemot with [Cacophosus Burst].
The victim · Olasird'arc Haylilyal · rank 15
The Frost Dragon Lord
From the royal palace of Feo Berkana he ruled Frost Dragons and Quagoa alike, and he had levelled the dwarven city of Feo Teiwaz fighting the dragon who then became his concubine. Faced with Ainz, he demanded the undead's equipment as the price of forgiveness. Ainz answered with [Grasp Heart] and he died on the spot, in front of his wives.
statedOverlord: The Dwarven Crafter · vol. 11, ch. 3
Feo Teiwaz was destroyed in his battle with Munuinia Ilyslym, who then became his concubine.
shownOverlord: The Dwarven Crafter · vol. 11, ch. 5
Is killed instantly by Ainz's [Grasp Heart] in the royal palace.
shownOverlord (anime) · S04E07
Dies to [Grasp Heart] while his three wives look on.
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.