Oh, no, Marvel! What have you done? Jean is an evil space goddess!/Wolverine is dead!/Cyclops is a murderer! Marvel has put its mutants in many bad situations over the years, but they always find a way to work around it. Here are just a few of many.
Back in 2014, Marvel killed the unkillable. The Death of Wolverine wasn't entirely shocking, but it did make long-time fans of the character wonder just where they'd be able to go to get their fill of Logan.
Marvel, of course, had the answer. No need to fret! They just brought in Old Man Logan to fill the void. Meanwhile, Laura Kinney, AKA X-23, donned the yellow spandex for those interested in the costume.
Jean Grey was dead for a pretty long time. After her meteoric rise to Phoenix and Dark Phoenix, she ended her own life to prevent herself from consuming the entire universe.
Once again, Marvel delivered in their own unique way. Beast travelled to the past and brought back the original X-Men: Cyclops, Iceman, Jean Grey, Angel, and Beast. Of course, this totally messed up the timeline (see Secret Wars for the results of all this meddling with time and reality) but who cares? We got our favorite telepath back, and a younger, happier and healthier X-Men team than we've seen in a while.
With his powers of teleportation, Nightcrawler can get out of the way of almost anything-except when he ends up impaled on the arm of his enemy. He spent some time in heaven along with Charles Xavier, until a demonic invasion led by his father Azazel led to his return to Earth (with a little help from the X-Men).
Back in 1967, the X-Men were shocked when the mentor, leader, and father figure of the X-Men died in battle against the alien Grotesk-except it wasn't actually him. Xavier had reformed a former foe, a shape-changer named Changeling, and had him pose as Xavier while Xavier planned for an alien invasion. This makes Changeling the first X-Man to fall in battle, but hey, at least Chuck lives on.
Kitty Pryde and the Future X-Men (And the Rest of Humanity)
In what's probably the second most famous X-Men storyline ever, humanity as a whole was headed down a very dangerous path. According to the famous Days of Future Past story, by 2013, North America would be ruled by the Sentinels, who attempted to eradicate all superheroes and interred all mutants in concentration camps. Thanks to some time-traveling by Kitty Pryde, however, the future Earth never came to pass for Earth-616.