I think something to consider would be that, while we as external viewers/readers to this character know that they are capable of anything, all they know is that they have yet to find something they cannot do. Similarly, they do not know that their power is flawless; say they use it to get information, they have no way of knowing for sure that it is 100% accurate.
The main consequence of this is that they could feasibly believe that there could be beings above them, even if their power tells them otherwise. To illustrate this further, consider the following scenario:
Let's say the Omnipotent creates a Nigh-Omnipotent, Nigh-Omnipresent, Nigh-Omniscient entity, whose only limitations are those surrounding Omnipotence (i.e., can't overcome it, achieve it, defy it, etc), whose only 'missing location', for lack of a better term, is whatever external place the Omnipotent is present in, and whose only missing knowledge is the existence of the Omnipotent being and the fact that they themselves are not actually Omnipotent. This being is created by the Omnipotent to fully believe that it is Omnipotent, even though it's not, but because it was created by the Omnipotent to believe so, it will believe this and never know otherwise unless the true Omnipotent being chooses to reveal itself.
So the question is, how does your character know that they aren't in that kind of situation? That their power isn't flawed or made so that it gives them false information, including about itself, so that they believe they are all-powerful? The answer is that they can never be sure, because any notion of certainty coming from their power is inherently rendered null and void if the validity of the power itself is the thing in question. This could potentially lead to paranoia, or something along those lines. They may even end up accidentally creating a being to fulfill this role of a 'greater entity' in their attempts to find evidence for one (in the sense that, because they can do anything, they can necessarily find evidence for an entity greater than themselves even if one does not exist), though naturally it would be, at most, Metapotent, simply because greater than Metapotence is Metapotence (in the same sense as 'greater than Omnipotence is Omnipotence').