4. Trevor Slattery
The Mandarin is one of Iron Man's biggest archenemies, so the idea of him being adapted for the MCU in Iron Man 3 was thrilling for fans of the comics. And then the fact that the great Ben Kingsley was playing the role only added to that feeling. But wow did Marvel Studios pull the rug out from under viewers.
In just a few short moments, all of that intensity that Iron Man 3 had built up was let out faster than air from a balloon when it was revealed that The MCU's Mandarian was actually just an actor named Trevor Slattery playing the role so that Aldrich Killian could make the world think he was a real threat. It was a twist reviled by comic book fans, particularly because of how silly the movie got whenever Trevor was on-screen, as the actor was oblivious to the seriousness of his actions.
Here's the thing with Trevor, audiences have grown to appreciate his humor and it all has to do with how well Ben Kingsley portrays him. His return in Shang-Chi And The Legend of the Ten Rings was quite well-received, especially because that movie introduced the real Mandarin, Wenwu. That said, fans have never fully gotten over the twist in Iron Man 3, seeing it as a move that robbed the movie of its own momentum and a poor attempt to adapt what could have been a major villain for the MCU.