We know from Guardians of the Galaxy 2 that Celestials are god like beings. Odin seems to possess a power far beyond any other Asgardian. He was a celestial that, unlike Peter's dad, used his power to birth a race of people who each carried a bit of his power within them.
In the cosmic hierarchy Odin is below celestials.
In general, no. Asgardians are physically twice as strong as your run of the mill Eternal, but they are not immortal, and Eternals are. Also Eternals directly tap into cosmic energy for a wide variety of powers, including telekinesis, telepathy, molecular transmutation, flight and more.
In fact, Thor is only half Asgardian. This will especially be news for fans who believe Thor's adopted brother Loki (a pint-sized Frost Giant) is the only non-Asgardian member of Odin's family (in the movies, that's a pivotal distinction).
IN THE BEGINNING
ETERNALS (1976) referred to the Celestials as “space gods,” but that doesn't mean they're gods as we define the term. However, they are cosmic beings of immense power whose size and scope defy human perception. They may not be the almighty, but they have directly influenced the course of human history.
The heroes try to stop the Progenitor several times, but their efforts are futile, as a Celestial is simply too powerful to be harmed or killed. However, this is not necessarily true. In fact, Thor owns a weapon that was created with the exact purpose of killing Celestials, and he used it effectively in the past.
Galactus Is More Powerful Than The Celestials.
Film. Arishem appears in Eternals, voiced by David Kaye. He is the Prime Celestial, credited for creating the first Sun and bringing light to the universe. His purpose is to expand the universe, which requires having to sacrifice lesser life forms to do so.
Peter Jason Quill was born in 1980 to Meredith Quill and Ego, making him a hybrid of human and Celestial. His conception was all part of a plot set up by his father to produce a second Celestial, whose power he could use to complete the Expansion, which involved assimilating millions of worlds into Ego's very being.
Is Thanos a Celestial? Strictly speaking, no. Thanos is not a Celestial. However, he is an Eternal.
Galactus would win in a fight against Odin.
Odin overpowers Thanos at almost every turn. He is more intelligent, durable, and faster, and his centuries of warfare led to more advanced combat skills. Thanos fears Odin due to his vast potential to utilize mystical powers, and when the two battled in the comics, Thanos lost by a huge margin.
Surtur, the fire demon, forges a sword called Twilight which would bring about the end of Asgard and Earth. Odin perishes many times facing him and ultimately gets caught in eternal combat with the demon.
During the "Time Runs Out" storyline, the Beyonders are revealed to have killed all the Celestials in each reality across the multiverse, to perform an experiment by destroying the Seventh Multiverse.
The Stone Age Avengers, led by Odin, were successful in defeating and burying the Mad Celestial when it arrived on Earth over a million years ago.
According to Loki, Odin speaks of Dormammu as an equal, whereas Dormammu considers Odin as an inferior. He has even dared to directly challenge Eternity itself, and in one case even overcame the entity. Dormammu even claims that he will destroy the Celestials, burning them in the Flames of the Faltine.
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.
When Ego was killed, Peter Quill lost his connection to the light that gave him powers presented in Guardians of the Galaxy Vol. 2. Even the director, James Gunn, revealed in a now-deleted Tweet that Peter isn't getting those powers back.
The Celestials were created by the legendary Jack Kirby in 1976. They were essentially envisioned as the ultimate Space Gods, who had seeded the potential for mutation and evolution within the human race countless millennia ago - and had done the same on countless other worlds too.
Dormammu isn't a Celestial. He is a Faltine which is a race consisting of beings of extra-dimensional energy born from pure energy. He resides in the Dark Dimension from which he can draw energy to augment his powers.
He is roughly the same size as a Celestial and feeds in a similar way, draining life from planets.
(A fun connection to Thor: Ragnarok is that Jeff Goldblum's Grandmaster is also a Celestial, just like Arishem and Kurt Russell's Ego from Guardians of the Galaxy, Vol. 2.
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.
Apocalypse states that the Hulk's power/energies can challenge or possibly even overcome the celestials themselves.
This is why Wanda's powers are so strong, but her genetic disposition - which may be the beginning of the development of mutants - also accentuates her abilities. Besides, Wanda's anger has increased her power level, and WandaVision just revealed that she now could hold her own against a Celestial.