The connecting record
shownundoneOverlord: The Bloody Valkyrie
Ainz Ooal Gown killed Shalltear Bloodfallen in Overlord: The Bloody Valkyrie.
under the World Item's control at the time; brought back afterwards with the treasury's gold
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 · Shalltear Bloodfallen · rank 2
Floor Guardian of the 1st to 3rd Floors
Caught Brain Unglaus's sword with almost no effort, and while a World Item was taking her mind, still put a holy javelin through the shield-bearer in front of its wearer and into the woman herself. Then, controlled, she drained Ainz's mana close to zero in a fight between two level-100s that was nobody's performance, and lost it. Second is where that leaves her: under the one entry that beat her, over everything that never had to try.
statedOverlord Wiki: Shalltear Bloodfallen/Abilities and Powers
Gives her total level as 100 in a status block transcribed from a character sheet, without saying which volume prints it.
Read the source for Overlord Wiki: Shalltear Bloodfallen/Abilities and Powers (opens in a new tab)statedOverlord: The Bloody Valkyrie · vol. 3, ch. 3
Shalltear is the strongest of the Floor Guardians, Gargantua excepted.
shownOverlord: The Bloody Valkyrie · vol. 3, ch. 2
Catches Brain Unglaus's God Flash with her fingertips.
All 6 citations
shownOverlord: The Bloody Valkyrie · vol. 3, ch. 2
With her Vampire Brides, kills the Death Spreading Brigade's mercenaries in their cave.
statedOverlord: The Bloody Valkyrie · vol. 3, ch. 5
Boasts, with Ainz's mana nearly spent, that her own health is still full.
shownOverlord (anime) · S01E10
Faces Brain Unglaus in the Death Spreading Brigade's hideout.
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.