There is nothing inherently wrong with extremely powerful and jerkass characters. Most scenarios actually have these in canon in form of deities or sentient high-level monsters. The question is how these characters are used.
They can be useful as:
- Villains (if not confronted directly)
- Questgivers (can't do everything on their own)
- Neutral NPCs which need to be persuaded to act in the interest of the players and solve some problems.
They should not be:
- The DMsGMs personal player-character so they can have a share of the playing-experience. This is not what DMingGMing is about and brings a whole heap of problems.
- The deus-ex-machina which ends up solving all the problems the players are supposed to solve themselves (sometimes a deus-ex-machina might be necessary to solve some serious screwups, but that should be an exception and not become a habit).
- The DMGM authority enforcement tool to bring divine punishment on every player who dares to act up.
The more they interact with the party directly the more problematic they become. Any combat encounter where they participate will be either unfair or boring (depending on which side they are) and serve no other purpose than to demonstrate their strength.
So you should try to persuade your GM to give their Uber-character more of an acting-from-the-background role in the campaign to avoid stealing the spotlight from the player-characters.