New Mutants Vol. 1 #35, X-Men Vol. 2 #25.And yes Magneto did defeat the Shadow King. You should read the comics.
New Mutants: he deflects Karma's posession attempt. Forgot about it, huh. No surprise there, though - it's Karma
So, Fatal Attractions. My position is: he was not resisting Xavier and Jean. He didn't even detect the attack. The whole point of what they were doing was walking around his mental defences, attempting to decrease his battle efficiency. In that, they succeed since Wolverine, of all people managed to get a shot at him.
Then Jean severed connection and Xavier promptly brutally mind-raped Mags.