Having seen Avengers: Endgame once before, this was actually the category I was most dreading. There's a lot of action in this film, and scenes with a lot of movement typically have the most trouble in this category as action in 3D can often make people queasy. Avengers: Endgame is unlike some of the earlier Marvel movies in this respect, as its action, even during scenes with a lot of characters moving at once, is very smooth and engaging in 3D. There is one scene early on in the movie that did feel too jiggly for a hot second, but it was during a quick moment of action and it was the only time I noticed this being an issue during the whole film. If we gave half scores in this column, I might bump it to a 4.5 because of that, but that's not enough of an issue for me to grade a 4 in this category, so 5 baby!