GalactusvsThanos

Galactus is the Devourer of Worlds, a cosmic entity who existed before the current universe and wields the Power Cosmic — an energy source that dwarfs nearly everything in Marvel. Thanos is an incredibly powerful Eternal with genius-level intellect and immense physical strength, but without the Infinity Gauntlet or other external power-ups, he operates several tiers below Galactus.

A well-fed Galactus can reshape reality, manipulate matter and energy on a universal scale, and has destroyed entire star systems as collateral damage. Thanos has fought Galactus before and knows better than to challenge him directly without cosmic artifacts. Even with his energy projection and near-immortality, Thanos is an ant compared to a fully powered Galactus.

The only scenario where Thanos wins is if he has the Infinity Gauntlet or has absorbed some comparable cosmic power source. In a standard encounter, Galactus could atomize Thanos with a thought.