The connecting record
statedThe Immortal Hulk · 2019
The One Below All killed Galactus in The Immortal Hulk.
revealed after the fact; the panel never shows it
What each of them is ranked on
The killer · The One Below All · off the scale
The thing behind the Green Door — comics
The other end of the same being. It lives at the bottom of the Below-Place, it wants everything that exists to stop, and its route into this universe is the Hulk: every gamma death goes through its door and comes back wrong. It is up here rather than ranked because it almost never acts as itself — it works by possession. In one far-future timeline it wore the Hulk as the Breaker of Worlds and killed Franklin Richards, then Galactus, then everything else, because what it wants is to be alone.
statedThe Immortal Hulk · 2018
Named as the inverse of the One Above All, dwelling at the base of the Below-Place.
shownThe Immortal Hulk · #25
In the far future it kills Franklin Richards, Galactus and Mister Immortal, until nothing else is left alive. — 2019
shownThe Immortal Hulk · 2021
Possesses the Leader, who has stolen Banner's body, and is fought directly when it manifests.
The victim · Galactus · rank 10
Galan of Taa — comics
A planetary death toll accumulated steadily across billions of years, framed by the books as metabolism rather than malice. Enormously destructive and almost never in control of anything, including himself, which is a different problem from the ones ranked above him.
statedFantastic Four · #48–50
Introduced preparing to consume Earth, with the worlds already eaten described rather than seen. — 1966
statedThor · #168–169
Given an origin as Galan of Taa, the sole survivor of a world killed by plague. — 1969
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.