8. Iron Man 3
The Trailer: Iron Man 2 admittedly was not the greatest of sequels but coming off of The Avengers there was seemingly a lot of interesting routes for Tony Stark's character to go. The trailer implies some heavy dramatization and more mature subject matter similar to Nolan's Dark Knight trilogy. Trailers also hyped up a mysterious villain dubbed the Mandarin whom fans eagerly awaited to see in action. Iron Man 3 was shaping up to one of Marvel's best films judging from the tense action and thematic elements of loss.
Why It Is Terrible: Everything I just mentioned was thrown away in favor of tarnishing source material for a twist that added some social commentary to the film. Tony's hilarious one liners and comedic presence were still intact but none of the villains were allowed to shine or be of remembrance. Instead it is a disjointed miss of a superhero film full of wonky plot structure.