The connecting record
shownOverlord: The Half-Elf Demigod Part II
Antilene Heran Fouche killed Decem Hougan in Overlord: The Half-Elf Demigod Part II.
her father, already drained by Ainz
What each of them is ranked on
The killer · Antilene Heran Fouche · rank 10
Zesshi Zetsumei — Extra Seat of the Black Scripture
Killed the Elf King, her own father, after he had spent his mana against Ainz and run. Against Mare minutes later she used everything she had: a copy of the Eclipse class's instant death, borrowed through her scythe, and a summoned Einherjar. Neither was enough. Placed on the duel rather than on the kill, which Ainz had half done for her.
shownOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Kills the Elf King, her father, after he flees from Ainz.
statedOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
The Elf King reaches her with his mana already spent against Ainz.
shownOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Uses a copied [The Goal of All Life Is Death] and an Einherjar against Mare.
All 4 citations
shownOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Loses consciousness to Mare and is taken prisoner.
The victim · Decem Hougan · rank 11
The Elf King
Killed the vice captain of the Holocaust Scripture with a summoned Behemot, and set the same creature on Ainz — who took it for a Primal Earth Elemental, a summon he had believed out of reach by normal means. Reading him mid-fight, Ainz judged his health comparable to a level-70 player's, then held him off behind walls of skeletons, lowered them, and destroyed his Behemot; lacking the mana for another attack, the Elf King fled. The estimate and the result agree, which is the pattern this page is about.
shownOverlord: The Half-Elf Demigod Part I · vol. 15, ch. 2
Kills the Holocaust Scripture's vice captain Schoen by summoning Behemot.
shownOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Summons Behemot against Ainz in the palace.
statedOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Ainz takes Behemot for a Primal Earth Elemental, which he believed could not be summoned normally.
All 5 citations
statedOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Ainz judges his health comparable to that of a level-70 player.
shownOverlord: The Half-Elf Demigod Part II · vol. 16, ch. 5
Lacking the mana for another attack, runs for the exit behind Ainz.
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.