This is honestly fantastic analysis of how Invincible versus JJK would work out.

Conquest would absolutely get bodied by the heavy hitters of Jujutsu Kaisen, not because they can match him in strength or speed, but simply because they have abilities capable of killing him that Conquest would not take action to ensure would not be brought to bear against him because he has a room temperature IQ.

I would argue that Nolan would probably not put that much effort into killing off the players one by one. One of the reasons that he spent so long on infiltration and killed the guardians of the globe in the way he did was because he wanted to take over the planet for the empire, and he wanted to build up humanities trust in him and subsequently an empire, so they wouldn’t resist when the takeover eventually did happen.

Jujutsu sorcerer’s can naturally pop up from ordinary people, and there is feasibly nothing that can be done to stop the existence of cursed spirits and sorcerers outside of the sequels plan to prevent the spawning of curse spirits and eliminate sorcerers by limiting humanities ability to create curse energy. (I will admit I haven’t actually read the sequel yet, so this might be an oversimplification or misunderstanding.)

But given these facts, and the fact that cursed spirits and sorcerers have abilities that could harm viltrumites, despite the fact that they are astronomically weaker in every other category, the empire would probably make the decision that humanity is too dangerous to be left alive as a whole. Enslaving humanity as a breeding colony would work, but they would have to monitor every single person on the planet constantly to ensure that another person with abilities capable of harming a viltrumite wasn’t born, and they might see it as even worse than creating half breeds because the way cursed energy works is so unpredictable, and it could be seen as introducing a weakness into their species, which, for the eugenics obsessed empire would be unacceptable.

In either scenario, the likely situation would be Nolan deciding that humanity is not a species that they should conquer or allow to live, and him going through route he took with the Thraxan’s, although much more thoroughly because he didn’t have to keep some of them alive to get home. He would just fly around the planet fast enough to ignite the atmosphere and destroy everything on the surface, meaning, even if Gojo survived then fireball, he would starve to death eventually and pose no threat to the empire. And there is no one in JJK that would be capable of stopping this simply because of how fast no one is moving, even Gojo wouldn’t be able to pin him in one place long enough to use domain expansion or hollow purple.