Thanos acquires the fully powered Infinity Gauntlet in The Avengers: Infinity War, but loses when all the superheroes team up together to stop him.
That does make sense and seems to fit what we know about them. Thanks for the clarification.They're likely not going to lose their power, just their connection to Eos. The whole point of killing the Astrals was to prevent them from giving Noctis their blessing which is essentials for his Ascension. The empire obviously didn't like the idea that some one was getting more power than them. So by killing the Astrals, Luna could no longer converse with them to ask for their power. Gentinia is a special case since she's one of the Astrals that actually like humans and is willing to go out of her way to give Noctis her blessing despite being 'dead'. The other Astrals wouldn't even bother.