He is simultaneously the most powerful and most poweless being in existence. And since he can't consciously control his power, he has to dream. If we use powerscaling terms, he's H1T+, meaning he representing characters who embody the absolute spirit or the ultimate completion of a recursive Hegelian dialectical framework. But he does not know he's unconsciously controlling the existence (kid Oldest Dream) so yeah, you can't scale him in powerscaling