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 ? Could God solve an unsolvable mathematical equation ? 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 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, or even fight it alone. However, through his own power he was able to create beings who helped him to finally defeat The Darkness.
 * The Darkness - While the true extent of The Darkness' power has yet to be revealed, it was credited by Death that it took God himself and His Archangels to defeat and seal it away. However she isn't fully omnipotent, as it couldn't defeat God and his Archangels.
 * Death - Death holds immense power which is far greater than Archangels and was possibly on par with God. However, he isn't omnipotent given that there are many things he can't do, e.g. Break souls, kill a person bearing the mark of Cain, etc.

Extremely powerful
Entities of immense power, that can apparently warp reality or destroy and create things to a limited extent.
 * Castiel (temporarily) - Castiel's powers were exponentially magnified as a result of having absorbed millions of souls from Purgatory. It was implied that he was still significantly weaker than God, as Death said that Castiel was no God even with 40,000,000 souls. At this level of power, Castiel could (supposedly) erase Hell from existence and annihilate lower Archangels with a snap of his fingers. It's currently unknown if he could have destroyed Michael and Lucifer.
 * Archangels - Archangels have a tremendously vast supply of power, they can accomplish incredible feats of power such as, e.g. obliterating common Angels, banishing common Angels etc. with gestures, finger snaps, winks or even simple thoughts. However there is still much that they can't do, examples include but are not limited to; freeing themself from some spells (Kalis blood spell), localize humans who are protected by enochian sigils, a forced possesion of a vessel or breaking out of Lucifer's cage.
 * Jesse Turner - Fueled by Lucifer's presence on Earth, Jesse has accomplished incredible feats of power such as, e.g. 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 height of his power, Jesse would have been able to destroy the entire host of Heaven with a single word.
 * 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 or recognize plots to overthrow him.