The connecting record
shownOverlord: The Men of the Kingdom Part II
Sebas Tian killed Zero in Overlord: The Men of the Kingdom Part II.
one heel drop, after letting Zero strike first
What each of them is ranked on
The killer · Sebas Tian · rank 7
Head butler of Nazarick
Let Zero, leader of the Six Arms, open with his strongest technique, took it without harm, and killed him with one heel drop — having already told him the four Six Arms who waited in the arena were dead. Earlier, inside an Eight Fingers brothel, he had killed Staffan Heivish after seeing what Staffan had done to a woman there. None of the Six Arms he fights in the arena lasts long enough to be measured.
shownOverlord: The Men of the Kingdom Part II · vol. 6, ch. 8
Lets Zero land his strongest attack, then kills him with a heel drop.
statedOverlord: The Men of the Kingdom Part II · vol. 6, ch. 8
Tells Zero he has killed the four Six Arms members waiting in the arena.
shownOverlord (anime) · S02E11
Kills Malmvist of the Six Arms in the arena.
All 4 citations
shownOverlord: The Men of the Kingdom Part I · vol. 5, ch. 5
Kills Staffan Heivish inside the Eight Fingers brothel.
The victim · Zero · rank 18
Leader of the Six Arms
Downed Lockmeier with one punch and had Brain, Climb and Lockmeier cornered with their rescue half finished. Then Sebas walked in, offered him the first blow, took his strongest technique without effect and killed him. His record is the gap between the two halves of one chapter.
shownOverlord: The Men of the Kingdom Part II · vol. 6, ch. 8
Downs Lockmeier with a punch and traps Brain, Climb and Lockmeier.
shownOverlord: The Men of the Kingdom Part II · vol. 6, ch. 8
His strongest attack lands on Sebas without harming him.
statedOverlord (anime) · S02E12
Offers Brain mercy if he will kneel and serve the Six Arms.
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.