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[Marvel] Why Is Galactus Allowed to Live When Defeated?

I have started digging into Marvel Lore. Currently their website is down and/or experiencing serious issues. But from what I remember Galactus can be defeated and he is allowed to live... possibly multiple times. From what I gleaned from the site before they put a new coat of paint on it and had failures, he had a discussion with Death and Eternity. The three decided he was likely a balancing force between Death and Eternity. This does not explain the rest of the MU occupants' motives for keeping him alive. Please explain why this hungry world killer is allowed to live.
gpt
The actual reasoning tends to change a little over time; the older explanation is that Galactus serves to maintain the balance in the universe between Death and Eternity (playing a comparable role to the In-Betweener and Lord Kaos and Master Order), or he plays some critical role in the universe - like keeping the cosmic entity Abraxas at bay. Of course, when Reed Richards let Galactus live, the rest of the galactic community didn't approve of that, which is why they put Reed Richards on trial.

In other universes, the reasoning is a little sketchier. In Earth X/Paradise X, Galactus (or equivalent Franklin Richards) acts as a counterbalance to the Celestials, to prevent them from multiplying too rapidly. In the Cancerverse, Galactus didn't serve any real purpose in a universe without Death and was turned into a literal engine of destruction.

As another note, the entire thing where Galactus went from Devourer of Worlds to Lifebringer and back again suggests his place in the cosmic hierarchy is not fixed.