Galactus is literally the Devourer of Worlds. He has even taken on four Celestials and defeated them by absorbing the powers of planets. After all, he can even bring back life to otherwise dead planets. He is also the oldest living entity of the Marvel Universe.
Enraged over the Celestials despoiling the Abyss through their creation of the 7th Cosmos, Knull manifested a blade of living abyss from his shadow – creating the first All-Black The Necrosword – and decapitated the Celestial, thereby marking it as the first death in the renewed Multiverse.
The Celestials, along with many of the Marvel Universe's abstracts, are killed by the Beyonders when these beings mount their attack on the entire multiverse.
Similarly, another Celestial - the Fallen - came to Earth in 1,000,000 BCE, and was defeated/killed by the Avengers of that time (Odin, Black Panther, Phoenix, Starbrand, Iron Fist, Agamotto, and Ghost Rider).
While recounting his origin to Eddie Brock, the Symbiote God Knull revealed that he was the one who killed the Celestial whose head became Knowhere with the use of All-Black the Necrosword and used his head to create more symbiotes.
While most Celestials possess extraordinary power, Gamiel is the weakest of all of them. He is the same size as that of the Hulk and is the youngest of all Celestials. Gamiel got the moniker “Manipulator” because he caused the events that led to the 4 million year Kree-Skrull war.
The Trickster God Loki Laufeyson, AKA Loki, frees an infected Celestial, Zgreb the Aspirant, and uses Zgreb to kill Arishem and the other Celestials or convert them into the Dark Celestials. The Avengers defeat the Dark Celestials and help revive Arishem and the others.
Arishem was killed alongside the Celestials by Annihilus during his universal conquest.
For instance, in War of Kings, Black Bolt's battle with the Omega-level mutant Vulcan opened the Fault - a tear in the very fabric of Marvel's reality. However, destroying multiple Celestials with one bellow confirms that Black Bolt ranks above Hulk, Thor, and even the Sentry in terms of raw power.
Centuries later, Thor used the axe to kill Exitar, a Celestial that had been lured to Earth by the Apocalypse Twins, by cutting open his neck (in Uncanny Avengers #21, by Rick Remender, Daniel Acuña, and Dean White).
Galactus Is More Powerful Than The Celestials.
Apocalypse states that the Hulk's power/energies can challenge or possibly even overcome the celestials themselves.
Unfortunately, no Odin cannot take down a Celestial. How do we know this? Because he tried already when the 4th host of Celestials came back to earth to judge mankind. Odin and all the peoples of Asgard merged their consciousness into the Destroyer to try to make them leave and were utterly defeated.
When the Eternals became aware that Tiamut's birth would result in the destruction of Earth, they rallied together to prematurely end his life, averting the Emergence in the process by also subjecting himself to the Uni-Mind.
He was obliterated along his fellow Celestials by Thanos when he stabbed Black Bolt to death in order to use his destructive voice as weapon. The bones of The One Above All and the other Celestials were later used by Thanos to build a temple to live the rest of his infinite life.
They're beings capable of creating and destroying entire planets which just shows the magnitude of their power. Dormammu is stronger than some Celestials like Ego the Living Planet. For example, in Guardians of the Galaxy Vol.
In Doctor Strange 2, Black Bolt's mouth was removed by Scarlet Witch. Panicked, Black Bolt tied to speak, causing his brain to implode from the power of his own voice, which was still destructive as ever. However, Black Bolt would likely have annihilated Wanda with a single word.
Thor. Thor is one of the most popular powerhouses in Marvel and is also capable of destructive blasts of energy because of his control over thunder. Of course, Thor is much stronger than Black Bolt in physical strength, but he probably isn't as destructive as Black Bolt. Thor's powers are more concentrated.
After all, It's because some fans thought that Galactus is a celestial, but no. Galactus is not a Celestial. Both are considered space gods threatening to destroy the earth. Both are giants with unimaginable power and have very similar wardrobes in the comics.
Guilt-ridden over his betrayal to Arishem and his actions against his fellow Eternals, Ikaris leaves earth and flies into the sun, ending his life.
Tiamut is frozen and killed by being turned to stone - stopping the Emergence.
Arishem is one of two Celestials who have the right and ability to judge which planet's civilization will live and which will die. Arishem's function is to act as the leader of Celestial landing parties and has led all Four Celestial Hosts on Earth.
Quill becomes the leader of the Guardians of the Galaxy after they assemble out of necessity to stop Ronan the Accuser from destroying Xandar. He discovers that he is a Celestial hybrid and that his father, Ego, created him as a means to terraform planets.
Arishem, just like all the Celestials, would have no problem defeating Thanos – especially one without the Infinity Stones. Thanos was one of the strongest living creatures in the universe, granted, but he was far from an all-powerful entity like the MCU's Celestials.
Ikaris, the Overpowered Eternal
Ikaris (Richard Madden) is stronger than most Eternals, losing in sheer strength only to Gilgamesh.