Though the Marvel Cinematic Universe may be the most successful comic book movie franchise to date, it likely wouldn't exist without the success of the original X-Men, which kick-started the trend of movie studios buying up every comic property they could get their grubby mitts on. Over the last 15 years, the X-Men series has been through its share of highs and lows, from the consistency of Bryan Singer's efforts to the rather unfortunate sequels and spin-offs churned out by hack directors. As entertaining as the franchise is, it's had its share of issues, from betrayals of the source material to creative "flourishes" that nobody really wanted to see. Though many of these issues have at least been remedied with Days of Future Past's neat time travel reboot, they still linger in our minds as a painful reminder of how horrendously things can go south in the wrong hands. Here are 15 X-Men movie moments that pissed off the fans...