In the X-Men Cinematic Universe, Professor X. has the ability to mind control people. The only problem is, he can not mind control the antagonist of the movie, Magneto, because he wears a helmet that protects him from mind control. My question is, why didn't he use his powers to mind control one of Magneto's henchmen and have them take Magneto's helmet off? Then he could easily mind control Magneto, and many problems would be solved.
He actually tries something very similar in one of the X-Men movies, where he controls Sabertooth and has him grab Magneto by the throat during a standoff with police, where Magneto has taken all the police weapons and pointed them back at the officers.
Magneto responds by firing one of the floating guns and holding back the bullet from penetrating the police officer's head, until Xavier releases Sabertooth from his control.
Magneto isn't defenceless against his henchmen in any case and is regularly demonstrated to be much more powerful than they are. Also, if that helmet contains any metal (and it looks like it does), it's not coming off unless he allows it to.