It’s the perfect endgame.
The most powerful being that isn’t consensually assumed to be fictitious? That’s our good man God of course. In all times, Gods were viewed as the original beings, the most powerful force that can ever exist. Truly nothing could ever be a match for them! …But what if the player character can?
To provide them with the option to take a jab at a god. And to give them the possibility of actually taking its ‘hood. Nothing greater you can offer, except for a new perspective on power to match. A perspective that may bring into view previously unseen forces, those that are even further beyond.
That… is where you lay down the law. That is where you say “no mere mortal can beat this part of the game”.