Summary
Omnipotence:
Sometimes called "Unlimited Power," Omnipotents are characters that can literally do anything as they are considered the be-all and end-all of characters and most of the time, God. They are the absolute strongest beings in their respective fictional franchises.
In fiction characters can only be presumed omnipotent, as much like in theology it is impossible to prove. In the best case there can be an impressive definition.
Technically, according to the dictionary definition, omnipotence could simply mean "infinite in power" or "having very great or unlimited authority or power", meaning a term defining its standing in relation to a certain setting and its inhabitants.
However, given the highly logically self-contradictory nature of the "can do anything whatsoever" definition of omnipotence (see the above image for an example), within this Wiki even characters with the highest "0" ranking are only described as having "Questionable Omnipotence".
In addition, if an author simply mentions the word "omnipotence", this is obviously not enough to justify that some character remotely fulfills the requirements for Tier 0. Because the understanding of different authors can be very different, and the author should also make clear that the entity is totally qualitatively superior to everything else. Completely unlimited, not just playing on the same field as other powerful beings from that fictional verse.
For more indepth information, please read: https://en.wikipedia.org/wiki/Omnipotence
Notes:
In the Kabbalistic system there is a thing (God or one of the attributes of God) called Ain Soph. It means boundlessness.
This is a strictly philosophical and theological term. There are not important feats or bulky descriptions about superiority over logic (or anything else).
It is just an attempt to create a model of an Absolute God. It is boundlessness beyond all perspectives or any other concepts. Any description (including any words that we may provide here) will be limited.
Transcendence, increased scale, multiplication by infinity, or any other option is meaningless. Boundlessness already includes all of those actions and is still boundless compared with any such options in any way.
But in addition to Ain Soph there is also Ain. Absolutely "nothing". Not even boundlessness, not everything, not nothing, just "not". You can not say or think anything about Ain (any words and thoughts are limited), you can only keep silent about Ain.
The other major theological systems (Christianity, Islam, Buddhism, Hinduism) also have similar concepts.
Or to put it in simpler terms: Omnipotence has no relation to something like "A character just destroyed 100500 Omniverses".
In addition, a real life author (living within our reality) should logically not be considered a character within fiction in any sense.
For example, the fictional character Superman will exist no matter how many comics that somebody destroys, or if somebody "defeats" the author. No matter how many fanfiction stories about the death of Superman that are written, or even if the official authors decide to kill him in their works, this fictional character will likely continue to exist even after your and said authors' deaths.
To use another example, The Lord of Nightmares beat her "author" with a shovel, but this does not really mean anything. The fourth wall is a meaningless nonsensical concept. This only happened as a part of fiction, and it does not affect reality in any way.
In Short, Omnipotence is something that is completely contradictory and impossible to demonstrate or understand on any conceivable level. By it's very definition, it is something that cannot be used to measure a character, and claims of Omnipotence, no matter how complex or developed, should never be viewed as proof of Omnipotence.