X-Men: Days of Future Past

X-Men: Days of Future Past (2014) — A dystopian future where Sentinels have exterminated mutants. Wolverine's consciousness is sent back to 1973 to prevent Mystique from assassinating the Sentinels' creator. It works, and overwrites the events of The Last Stand, restoring Jean and Cyclops.

The Sentinels are adaptive robots that copy any mutant power used against them, which is why the future is unwinnable: every attempt to fight them makes them stronger. Kitty Pryde can send a consciousness back through time, and only Wolverine's healing factor can survive the trip across fifty years.

In 1973 he has to reunite a Charles who has given up — drugging away his telepathy to be able to walk — with a Magneto imprisoned under the Pentagon for the Kennedy assassination. The target is Mystique, whose assassination of the Sentinels' creator Bolivar Trask is what convinces the world the programme is necessary. Charles stops her not by force but by asking, on live television, and she chooses to walk away.

That choice rewrites the timeline. Wolverine wakes in a school where Jean Grey and Cyclops are alive, which is the film's real function: it lets both casts coexist and quietly deletes The Last Stand.