10) Half The Marvel Universe
First up, let’s go back to the comics. When Thanos gets his hands on all of the Infinity Stones, he uses his completed Infinity Gauntlet to wipe out half of all life in the universe – with a single snap of his fingers. It’s an iconic moment, and it would be amazing if it could be replicated on screen.
In The Infinity Gauntlet comic, Thanos’ actions result in half of the Earth’s superheroes simply blinking out of existence, which is what leads the Avengers to attack him. In other words, it’s the inciting incident of the whole story – one which perfectly demonstrates the staggering power at Thanos’ disposal.
Admittedly, if this was recreated in the movie, it wouldn’t have as much of an affect as it did on the page, as there are far fewer heroes running around the MCU. Plus, it would kind of defeat the idea of doing a mega franchise-wide crossover if half of the characters were missing. Still, it’s hard to think how they could come up with something that would top this.