Avengers: Infinity War is demanding, heartbreaking, exhilarating, massive, and dense. More than seemingly any movie so far in the Marvel Cinematic Universe, it requires its viewer to be intimately acquainted with all the films that come before it - and, if you are, it's rewarding and audacious in ways the franchise has never been before and isn't likely to be again. It's a movie that is not screwing around.