9. Hulk Becomes Sakaar's Champion - Thor: Ragnarok
Though Thor: Ragnarok lovingly incorporated elements of the beloved Planet Hulk comic storyline, many fans decried the fact that it was ultimately adapted in such a piecemeal fashion, effectively serving as a relatively minor portion of Ragnarok's story.
By the time we first see The Hulk (Mark Ruffalo) on the alien planet Sakaar, he's already a much-ballyhooed champion gladiator, when the journey getting to that point would arguably be much more interesting and entertaining.
Ultimately it would've been ideal for the MCU to simply adapt the Planet Hulk story in a more overt way, showing the Hulk's rise through the ranks as an unmatched combatant who wins himself a legion of adoring fans in the process.
A Planet Hulk movie styled as a parody of classic sports films could've been a lot of fun: an array of awesome gladiatorial combat crossed with a giddy satire of the cult of celebrity Hulk enjoys on Sakaar.
Sadly it feels like the boat has well and truly sailed on this one - especially with Marvel still not pulling the trigger on a solo Hulk film - though it's not entirely out of the question that we might catch a flashback to Sakaar in the upcoming She-Hulk series.