The connecting record
shownOverlord: The Caster of Destruction
Ainz Ooal Gown killed Gazef Stronoff in Overlord: The Caster of Destruction.
a duel Gazef requested, refusing resurrection in advance
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 · Gazef Stronoff · rank 17
Warrior-Captain of the Re-Estize Kingdom
On the night the Sunlight Scripture came for Carne Village he kept their angels off with martial arts until their magic wore him down. When he next met Ainz it was on the Katze Plains with an army dying behind him; he refused to serve, asked for a duel instead, and asked not to be revived from it. Ainz stopped time before he could move.
shownOverlord: The Undead King · vol. 1, ch. 4
Fights the Sunlight Scripture's angels and is overwhelmed by their magic.
statedOverlord: The Caster of Destruction · vol. 9, ch. 4
Refuses Ainz's offer of service and challenges him to a duel.
shownOverlord: The Caster of Destruction · vol. 9, ch. 4
Is killed by [Time Stop] and an instant-death spell before he can act.
All 4 citations
shownOverlord (anime) · S03E13
Cannot react to a Dark Young's missed tentacle strike before the duel.
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.