4. Apocalypse
I actually liked X-Men: Apocalypse, but yes, I'm well aware that I'm in the minority! I even thought that Oscar Isaac was pretty great as En Sabah Nur (despite being plastered in prosthetics), but at the end of the day, there's no denying that the character wasn't utilised to his full potential here. While he certainly served this particular story fairly well, this version of the iconic X-Men villain failed to live up to his comic book counterpart both in terms of his appearance - he really should have been a fully CGI creation - and the way his powers were portrayed.
Bryan Singer grounded him a little too much, and while he and writer Simon Kinberg did delve into his background to at least some extent, none of it was anywhere near as fantasical and big as it should have been. Ideally, this movie should have delivered an Age of Apocalypse type storyline, but thanks to the way he was dispatched with at the end of the movie, the chances of Apocalypse returning somewhere down the line now look to be somewhere between slim and none, and that's pretty unforgivable.