An action movie can only be as good as its climax. This is a genre that's all about building up a constantly growing feeling of thrill and excitement, and it's at the pinnacle of its narrative that it should engage viewers the most. The Marvel Cinematic Universe is no exception. Thankfully, the highest-grossing film franchise in history has had several climaxes that have gone down in history as some of the most unforgettable of the entire superhero genre.