Underrated pivotal entry to the franchise
Watched this again last night, with all that's happened since. This movie blended pure comic book action and imagery, with a laid back approach where you really get to know the character motivations. The AI element I think probably went over a lot of people's heads especially as it relates to the mind gem but it was pretty well handled. And importantly it set up a lot of what was to come with the MCU franchise.
It spelt out the Infinity gem plot
It established the Planet Hulk scenario
It established the Natasha/Bruce romance
It introduced Vision and Scarlett Witch
It established the conflicting motivations between Tony and Steve that would be the basis for Civil War
Gave Natasha a condensed origin story
It introduced Wakanda and how ridiculously powerful Vibranium is, setting up Black Panther
It possibly forshadowed the death of many of the Avengers in Infinity war (Tony is convinced he saw the future)
It introduced the Hulk-Buster
It more or less ended HYDRA
Set the stage for Zemo with the destruction of Sokovia but also the twin's similar motivations
It even introduced the question of what happened to the technology post-Avengers invasion that was the main plot of Spider-man Homecoming (ie how did HYDRA get the Chitauri worm)
This is possibly the most important movie plotwise and character-developmentwise in the franchise