@Godking25 A big part of what makes characters interesting is how they respond to challenges. But when trying to challenge Omnipotent-level characters, the challenges put before them really can't be external, because any such challenge could be trivially overcome. I'm suggesting a possible internal challenge they could face, one that could not really be overcome through Omnipotent-level power alone (I mean, it could be, because they could use their power to convince themselves that there isn't anything above them, but if they're paranoid about it then they likely wouldn't want to do that).
@Necropolis00 In essence, your character might wrestle with the idea that there could be entities more powerful than them in the same way some people have existential crises relating to the possibility that we are in a simulation, or something of that nature. It's something that they could neither prove nor disprove - or, in the case of a character with Metapotence, something they could both prove and disprove, since they can do anything.
While they could certainly use their power to gain the knowledge of whether or not there is anything more powerful than them (there likely wouldn't be, since they have Metapotence), they may still be uncertain because if there is something more powerful than them, it could entirely just be out of reach of their power, so their power can't recognise its existence and 'believes' itself the most powerful. A similar thing can be said about if they were to use their power to determine the full strength of their power. They would find out that they can do anything... but how do they know that the power isn't actually limited in some way and is just incapable of recognising its own limits? We know that they have Metapotence and so can do anything, but they could reasonably doubt that, even if their power tells them otherwise.
This could lead to a variety of things. Perhaps they become paranoid, and spend significant amounts of time preparing for a threat that isn't there. Perhaps they continually seek out higher levels of power that don't actually exist (though they could attain them all the same due to having Metapotence. Again though, any level of power 'beyond Metapotence' would be functionally equivalent to Metapotence, since Metapotence can already do anything). Perhaps they limit their actions in an attempt to 'avoid drawing attention to themselves', because they believe there could be things above them that would take notice if they started doing anything too extreme.
The furthest you could take this would likely be if they decided to find a being more powerful than themselves; they have Metapotence, so they can do anything, even this. They would inevitably succeed in finding something 'more powerful' than themselves, even if such a thing did not exist. Of course, as stated before, 'beyond Metapotence' would be functionally equivalent to Metapotence, so such a being would, at most, match your character in power (though your character may believe otherwise).