Filmmaker Matthew Vaughn has been plenty busy building out his own Kingsman franchise over the last few years, but once upon a time he was poised to direct multiple X-Men movies. The first X-Men film he was attached to was X-Men: The Last Stand, but he backed out before production began. He eventually directed 2011’s X-Men: First Class, which successfully rebooted the series and introduced a new, younger ensemble, but while he was originally set to helm the follow-up, he backed out and Bryan Singer returned to spearhead X-Men: Days of Future Past …