Superman 4

 Because of budget and other constraints this film was never done properly, though it could have been the biggest and most significant Superman film

During the 80s, everyone was wary of nuclear war, world war 3. There were all those films like The Day After

We knew the concept and threat of MAD - Mutually Assured Destruction In this reality, Kal El, on Earth, as Superman, has the power to step in and stop this.

In the first film we see Jor El tell him how he is forbidden to interfere in human history.

And we see Jonathan Kent tell him "You are here for a reason"

We see Clark, who has spent his whole life as a human on Earth, albeit concealing his abilities, trying to decide how much Superman can or should get involved, or more so, how much should Superman interfere Finally we see him go to the UN to announce his decision that he will rid the Earth of nuclear weapons, removing the possibility of WWII, of MAD, taking that decision away from the human race Superman announces that he is no longer a visitor, he is now a citizen of Earth. Clark has spent his whole life as a citizen of Earth, though nobody knows this The power to destroy the earth in nuclear Armageddon does not actually lie in the hands of the human race anyway, it is in the hands of a few politicians who control the weapons. The citizens of earth would not wipe each other out, but their elected leaders may, and there in no plan for unilateral disarmament, and we know, forty years later there never has been So Clark, who would survive a nuclear war, unharmed, left in whatever the new world would be, makes his decision. He puts on the suits and goes, as Superman, to announce this decision to the world He does not consult with the governments, the leaders, he doesn't need to. He will simply fly to each country, take the weapons, and dispose of them in space It's actually a remarkable story, and only Christopher Reeve could have played this version of Superman, with this storyline It's a fitting tribute to him that this version of Superman changed the world for the better and gave the human race a better future