9. Creative Control Over His Movies - Edward Norton
The curious case of Edward Norton's all-too-brief tenure in the MCU sure is fascinating.
If you know much about Norton at all, you'll be aware that he likes to exert a large degree of creative control over the projects he appears in, and this extended even to his initial role as Bruce Banner in the MCU.
Norton made his first and only appearance as the character in 2008's The Incredible Hulk, where he was given the latitude to rewrite Zak Penn's original script, though ended up coming to blows with Marvel over the movie's final cut during post-production.
This led to Norton being absent for much of the movie's North American publicity tour, and with it being clear that he simply required more creatively than Kevin Feige was willing to give, the producer decided to dismiss Norton from the role.
Or if you believe Norton's account, he walked away.
Either way, Norton was replaced with Mark Ruffalo, who effortlessly picked up the mantle and has received consistent acclaim for his performance in the role ever since.
As brilliant an actor as Edward Norton is, expecting to have major creative control in such a massive ensemble enterprise comes off as either arrogant or naive, and had he stayed aboard for future films the clashes likely would've only become more intense.
Feige probably made the right call for everyone involved, honestly.