James McAvoy in the movie X-Men: First Class.

Pictured: James McAvoy portrays Charles Xavier, a powerful telepath who can read and control minds.
X-Men: First Class Movie Synopsis: Charts the epic beginning of the X-Men saga, and reveals a secret history of famous global events. Before mutants had revealed themselves to the world, and before Charles Xavier and Erik Lensherr took the names Professor X and Magneto, they were two young men discovering their powers for the first time.

Not archenemies, they were instead at first the closest of friends, working together with other Mutants (some familiar, some new), to stop Armageddon. In the process, a grave rift between them opened, which began the eternal war between Magneto’s Brotherhood and Professor X’s X-Men.