A new Marvel fan theory suggests that the villain of the fifth Avengers movie could be none other than Hulk himself. The theory is based on a comic book run called World War Hulk, in which the character became resentful towards his former allies such as Tony Stark and Doctor Strange, and vowed to take them down.
In the Marvel Cinematic Universe films, Bruce Banner aka The Incredible Hulk has had multiple interactions with both Tony and Dr Stephen Strange. In the second Avengers film, Tony confided in Bruce about his Ultron goof-up, while in Avengers: Infinity War, Bruce landed at Doctor Strange's doorstep after being defeated by Thanos.
The theory, posted on Reddit, suggests that Bruce, after losing Natasha Romanoff in Avengers: Endgame, and having Tony take the credit for defeating Thanos while his contributions -- Hulk was the one who was chosen to wear the prototype gauntlet designed by Stark -- were forgotten.
The theory speculates that combined with the loss of Natasha and the resentment he feels towards Tony -- both are plotlines that are touched upon in the World War Hulk comics -- Bruce might transform into a villainous character in Avengers 5.
Avengers writers Christopher Markus and Stephen McFeely recently revealed that Bruce might not be as in control of his Hulk persona as he claims he is. They said that after snapping his fingers, he was transported to the Soul world, where he Smart Hulk came face to face with Bruce. "We did write one," the duo said, "a conversation between Hulk and Banner, but it didn't make it to camera. Ruffalo showed up but Hulk wouldn't come out of his trailer."