If Tony Stark's greatest psychological shadow in a normal universe would undoubtedly have come from the final boss, Thanos, then in this universe, what Tony Stark feared most was unquestionably the Celestials. Even Darkseid had to fall a step behind them!
After all, compared to Thanos, who wanted to wipe out half the population of the universe, and compared to Darkseid, who had set his sights on Earth tens of thousands of years ago, the Celestials' connection to Earth was undoubtedly much deeper.
After all, in this universe, Earth's civilization—and even the vast majority of civilizations in the universe—had been initiated by the Celestials. Earth itself was even one of the Celestials' experimental grounds. That was something Earthlings simply could not accept.
It could be said that what the Celestials had done was even more chilling than the gods treating Earth like a pasture, because during the Age of Gods, even ordinary people knew the gods existed, but the Celestials were not known to anyone.
They were like a group of observers. They would not really act against Earth much, yet no one knew when they might completely destroy all of Earth's civilization.
That feeling was like a Little Boy observing an ant colony. Perhaps he was very interested in the colony right now, but no one could guarantee that in the very next moment, the Little Boy would not simply step on the colony, or burn it with fire, or soak it with a stream of urine...
Especially since the ants within the colony had no idea what the Little Boy was thinking. What was more, the Little Boy Earth now faced was not just one person.
Therefore, even with a powerhouse like Robet holding down the fort on Earth, Tony Stark still had no real sense of security.