There are still 4 months for Avengers EndGame and fans are just suggesting theories about what all could possibly happen in the movie and how can the Avengers defeat the almighty Thanos.
Well, a theory by juckingstar209 a Reddit user says that Avengers will take Thanos in the Quantum Realm and imprison him in there. The theory goes something like this.
Scott Lang will gain knowledge about the Quantum realm as he is in there and will seek out Avengers after coming out(as shown in the trailer). Where he says Avengers to take him to Quantum Realm and fight him. Because Thanos can’t use his powers(Infinity Gauntlett) in Quantum Realm. Because Infinity Stones power work in the original universe and Quantum Realm is an Alternative universe. With no Space and time in there Thanos can’t use Infinity Stones and will be defeated and imprisoned in there.
After this Thor will be the one who reverses the Decimation, and will bring all the dead Asgardians including Heimdall and Loki, if he could convince Doctor Strange. But how will Scott get a knowledge of all this in a short time while it took years for Janet to understand it. Well we all know she was in his head even when she was in an alternative universe (Quantum Realm). So it could be possible for her to get in her head once again.
There are chances of the theory to be right. Because Actor Benedict Cumberbatch said that Quantum Realm will be at the center of the Movie. And some leaks also gave us a suit similar to Hank Pym’s which says that this theory could be True. Without any Time Travel Avengers can defeat Thanos and also Imprison him in Quantum Realm.
Because Quantum Realm will give Avengers some unwanted energy and Pressure which could also kill them, so they do need a Suit and the leaks gives it.
This was just a Fan theory, if fans want to know what happens, you have to wait for the movie. 26th April, 2019.