The newest trailer for Avengers: Infinity War highlighted one specific change that the new movie will make to the Infinity Gauntlet comic that inspired it.
The Marvel Cinematic Universe has only ever used its comic predecessors as a starting point to tell new and different stories.
He’s going to wipe out half the universe because he doesn’t feel the universe is currently in balance.
Gamora mentions that if Thanos gets all the Infinity Stones he can wipe out half the life in the universe with a snap of his fingers.
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Avengers: Infinity War Trailer Breakdown - All the Easter Eggs and Secrets