X2: X-Men United

Essential, and the best of the original three. It takes the thing the first film established and raises the stakes properly: a military programme run by a man who considers mutation a disease, a raid on a school full of children, and an alliance with the villain because the alternative is worse.

The opening is the series' high point. Nightcrawler teleporting through the White House in a single apparently continuous sequence is a self-contained short film, and it does more character work than the plot that follows, because the film then reveals he was being controlled and is horrified by it.

The scene most people remember has no action in it. Bobby Drake tells his parents he is a mutant, they react badly, and his mother asks whether he has tried not being one. The film does not comment, and it did not need to. Its screenplay drew on a 1982 comic about a televangelist campaigning against mutants, and the politics survive the adaptation.

Brian Cox's Stryker is the best antagonist in the Fox run, a man with a specific private grievance dressed as policy. It ends on a death that the next film spends two hours mishandling. Watch it directly after the first.