Who beheaded the celestial that became knowhere?

Question

Guardians of the Galaxy did a lot for the MCU. It presented a likable group of rag-tags to audiences, introduced the universe's cosmic corner, and inadvertently created one of the franchise's most intriguing mysteries. Halfway through the movie, the Guardians traveled to a mining colony called "Knowhere". As Gamora explained, the colony was built inside the severed head of a Celestial, an ancient being of seemingly unlimited power.

Gamora's explanation made several fans and me curious about the alien's beheading. After all, what kind of being is powerful enough to take down and dismember a Celestial?

I know the answer from comics point-of-view, but is there any information in the MCU on this?

Answer 1

In the MCU...

We don't know

After all, what kind of being is powerful enough to take down and dismember a Celestial?

Logically, another Celestial or equally (if not greater) powered entity.

Few if any of these have yet shown up in the MCU^1/2 (except Ego and casual reference to others) but, at least in the comics, there are several.

^{1. I exclude Galactus from the Fantastic Four movies as this is/was not an MCU movie}

^{2. There is reference to Eson the Searcher in GotG who is also a Celestial}

A brief rundown of the top 16 powered comic entities can be found here.

Again in the comics there was a civil war between celestial-level entities including a "Godkiller" weapon.

The two opposing factions of the First Firmament's children could not peacefully co-exist and the ensuing war nearly destroyed the first universe. At some point during the war, the Aspirants created a now-lost hyper weapon called the Godkiller, a space-borne 25,000 foot (7,600 m) tall humanoid robot that dwarfed even the Celestials themselves. It was powered by a cosmic artifact later called the Heart of The Voldi (named after the species which would adopt it) and operated by genetically engineered pilots. During the war, the Godkiller destroyed countless billions of Celestials and brought them to the brink of extinction.

Wikipedia