X-Men : Legionquest
Scott Lobdell, Mark Waid, Fabian Nicieza et Collectif1995

Charles Xavier -- The world's foremost expert on mutants, and an incredibly powerful telepath, he has devoted his life to creating a world where mutantkind might co-exist peacefully with their human brethren. A noble goal all too often opposed by one of his own kind.
Magneto -- Once friend to Xavier and ally to his dream, this magnetism has since come to see humanity as an inferior and aggressive strain of life which will ultimately destroy mutantkind to protect itself. So convinced is he of mutantkind's doomed destiny, he will eventually become Xavier's greatest nemesis.

Enter Legion -- Xavier's psychologically unstable son. This dangerously powerful mutant has traveled twenty years into the past on a mission of vengeance to earn the love and admiration of the man he respects the most -- his father -- by insuring that the events of history never come to pass.

Unfortunately for reality as we know it -- he will succeed.
(Collects Uncanny X-Men #320-321; X-Factor #109; X-Men (vol. 2) #40-41, Cable #20)