Omnipotence

There are different definitions for Omnipotence: The problems occur by asking questions like "Could God make a stone so heavy he can no longer lift it ?" If he can't do it, then he is not omnipotent because he should be able to create such a heavy stone, if he can do it, then he is not omnipotent, because he can't lift the stone. There are many variations of the problem, for example: Could God create something stronger than himself ? As no character in the Supernatural Universe is omnipotent by either of these two definitions, no such problem has arisen on Supernatural.
 * The ability to do anything non contradictionary. This definition prevents logical contradictions.
 * The ability to do anything, this definition leads to logical contradictions.

Omnipotence
No being in the Supernatural universe is truly omnipotent in the sense of the common definition of the word.

Nigh-Omnipotence
True God-Like entities of nearly unlimited power that can create conscious beings, new realities or at least warp them to an unlimited extent.
 * God - God possesses near-infinite power, being able to do almost anything that he desires. It is shown that he isn't fully omnipotent, as he can't kill the Darkness. However, through his own power, he was able to create beings who helped him defeat her.
 * The Darkness - While the true extent of The Darkness' power has yet to be revealed, it was credited by Death that it took God and his Archangels to defeat and seal it/her away. However, she isn't fully omnipotent, as she couldn't defeat God and his Archangels. Lucifer has stated that her power is equal to God's.
 * Death - Death holds immense power which is far greater than Archangels. According to himself, he would reap God at the end of time. However, there are many things he can't do.

Lower Tier Nigh-Omnipotence
Entities of nearly unlimited power that are weaker than the top tier.
 * Archangels - Archangels have a tremendously vast supply of power, they can accomplish incredible feats of power such as obliterating abd banishing common Angels with gestures, finger snaps, winks or even simple thoughts. However, there is still much that they can't do: find humans who are protected by enochian sigils, forced possesion of a vessel, or breaking out of Lucifer's cage.
 * Castiel (temporarily) - Castiel's powers were exponentially magnified as a result of having absorbed all the souls from Purgatory. At this level of power, Castiel could annihilate lower Archangels with a snap of his fingers and (supposedly) erase Hell from existence.
 * Pagan Gods (formerly) - as said by Sam, the Pagan Gods were once "...just short of invicible" thanks to the sacrifices of their followers. But as the humans don't believe gods no more, their power has significantly decrease.

Extremely powerful
Entities of immense power, that can apparently warp reality or destroy and create things to a limited extent.
 * Metatron - Empowered by The Word of God, his angelic powers were greatly enhanced and common angel defenses like angel blades proved to be ineffective against him, but he was still far from being omnipotent since he was dependent on the Angel Tablet, and could not kill the bearer of The Mark of Cain.
 * Jesse Turner - Fueled by Lucifer's presence on Earth, Jesse has accomplished incredible feats of power such as exorcising a demon by verbally telling them to leave their host, turning an Angel into a figurine, conjure beings into existence simply by believing in them, etc. According to Castiel, at the peak of his power, Jesse would have been able to destroy the entire host of Heaven with a single word.