Your main hero cant be just invulnerable to everything and never get hurt. Having amnesia isnt a kryptonite.
Your bad guy cant be just a total jerk who can be trivially beaten as soon as you've had enough. You bad guy needs to be the baddest of them all with the essentially no weaknesses. That 1 weakness and how they'll be defeated is that optimistic view of the future.
My fun twist in my third book. The main hero comes back to earth on a superpower alien battleship. Absolutely nothing anyone can do about it.
He bluffs that his plan to be emperor on earth and that his first action is to end all violence. That all violence is banned and he's judge jury and executioner from orbit. If violence detected his battleship blasts the criminal and vapourizes them.
But its a bluff, so it's 1 timezone at a time so criminals might not catch on easily and he puts on a show where criminals and named and vapourized on the show. But its all machine ai produced. There are actual shots down to earth which make lightning like booms and leave craters; but nobody is actually hurt.
Slowly but surely violence ends on earth. Then I make my predictions on what life is like when people never fear violence.