See SFMZ's page on The Last Stand for all characters in the X-Men trilogy.
Throughout 1989 and 1990, Stan Lee and Chris Claremont were in discussions with James Cameron and Carolco Pictures for an X-Men film adaptation. The deal fell apart when Cameron went to work on Spider-Man, Carolco went bankrupt, and the film rights reverted to Marvel Studios.
In December 1992, Marvel discussed selling the property to Columbia Pictures to no avail. Meanwhile, Avi Arad produced the animated X-Men TV series for Fox Kids. 20th Century Fox was impressed by the success of the TV show, and producer Lauren Shuler Donner purchased the film rights for them in 1994.
Andrew Kevin Walker was hired to write the script in early 1994. Walker's draft involved Professor Xavier recruiting Wolverine into the X-Men, which consists of Cyclops, Jean Grey, Iceman, Beast, and Angel.
The Brotherhood of Mutants, which consisted of Magneto, Sabretooth, Toad, Juggernaut and the Blob, try to conquer New York City, while Henry Peter Gyrich and Bolivar Trask attack the X-Men with three 8 feet (2.4 m) tall Sentinels.
The script focused on the rivalry between Wolverine and Cyclops, as well as the latter's self-doubt as a field leader. Part of the backstory invented for Magneto made him the cause of the Chernobyl disaster. The script also featured the X-Copter and the Danger Room. Walker turned in his second draft in June 1994.
More scripts were written by John Logan, James Schamus, and Joss Whedon. One of these scripts kept the idea of Magneto turning Manhattan into a "mutant homeland", while another hinged on a romance between Wolverine and Storm.
Whedon's draft heavily featured the Danger Room, and concluded with Jean Grey dressed as the Phoenix. According to Entertainment Weekly, this screenplay was rejected because of its "quick-witted pop culture-referencing tone", and the finished film contained only two dialogue exchanges that Whedon had contributed.
In 1996, Fox approached Michael Chabon to write a script. Chabon's six-page film treatment focused heavily on character development between Wolverine and Jubilee. It also included Professor X, Cyclops, Jean Grey, Nightcrawler, Beast, Iceman, and Storm. Under Chabon's plan, the villains would not have been introduced until the second film.
In 1944 German-occupied Poland, a 13-year-old Erik Lehnsherr is separated from his parents upon entry to a concentration camp. In attempting to reach them, he causes a set of gates to bend towards him, as though attracted by a magnetic force.
Decades later, in the not too distant future, Senator Robert Kelly attempts to pass a "Mutant Registration Act" in Congress which would force mutants to publicly reveal their identities and abilities. Present are Lehnsherr, now known as Magneto, and the telepathic Professor Charles Xavier, who privately discuss their differing viewpoints on the relationship between humans and mutants.
In Meridian, Mississippi, 17-year-old Marie D'Ancanto accidentally puts her boyfriend into a coma upon kissing him which was caused by her unknown superhuman ability to absorb the life force and mutant abilities of anyone she touches. In fear that she is harmful, Marie, now going by the name of Rogue, runs away to Laughlin City, Alberta.
While at a bar, she meets Logan, an amateur fighter known as "Wolverine", who also possesses superhuman healing abilities, heightened senses, and metal claws that extend outwards from between his knuckles. While on the road together, both of them are attacked by Sabretooth, a fellow mutant and an associate of Magneto.
Cyclops and Storm arrive and save Wolverine and Rogue, and bring them to the X-Mansion in Westchester County, New York.
They are introduced to Xavier, who leads a group of mutants called the X-Men, who are trying to seek peace with the human race, educate young mutants in the responsible use of their powers, and stop Magneto from escalating the war with humanity.
Senator Kelly is abducted by Magneto's allies Toad and the shapeshifter Mystique and brought to their lair. Magneto uses Kelly as test subject of a machine that artificially induces mutation. Kelly uses his new mutant abilities to escape imprisonment.
After an accident causes Rogue to use her powers on Wolverine, she is convinced by Mystique (disguised as classmate Bobby Drake) that Xavier is angry with her and that she should leave the school. Xavier uses his mutant-locating machine Cerebro to find Rogue at a train station. Mystique infiltrates Cerebro and sabotages the machine.