All of those fallen Marvel characters have important implications for the future of Marvel; these are the characters who almost certainly won’t be showing up in future Marvel Cinematic Universe movies.
Unless who dies (or stays dead) in the movie is not a spoiler in your opinion. Then you’re fine.
The following post contains SPOILERS for Avengers: Endgame.
We have also included a way every single character could be brought back to life despite their current not-alive status.