Captain America: Civil War
It has so many heroes but still manages to fit them all into the story organically, give them their time to shine, and keep the pace of the story moving along. It's a huge accomplishment and I can't believe they pulled it off successfully.
It's about two and a half hours but it doesn't waste any of it. Civil War never feels like it drags or slows down too much. It keeps moving and stays interesting throughout. From the tense conversations to the direct confrontations it held my attention the entire time.
It feels like they earned this movie through a lot of hard work and set up. It doesn't feel phoned in or cheap. It was visceral and difficult to watch this team we know tear itself apart. This is the benefit of setting up the MCU with so many movies before making the heroes come to blows with each other.
Not only do they manage all this, but they also successfully introduce both Black Panther and Spider-Man in interesting ways. Now I really want to see solo movies for both of those heroes!
If you've generally kept up with the Marvel Cinematic Universe until now you need to see this entry. It's amazing.