As one of the smartest heroes in the entire Marvel universe, Professor X has as many clever moments in comics as the X-Men have members - which is to say, a whole damn lot.
Even with his powers removed, the psychic has four PhDs, and a Medical Doctorate in Psychiatry, meaning he's an intellectual heavyweight even without his brain-boosting powers in mind.
Combining his telepathic abilities with a considerable intellect and thirst for knowledge, Charles Xavier is capable of out-planning and outsmarting just about anyone, given the right amount of time and resources. There are few enemies of the X-Men who haven't bore the brunt of Xavier's acumen, and even fewer who don't regard the telepath as a massive threat due to his cerebral wiles.
While the mental heavyweight isn't a stranger to creating bad plans, even his more immoral or questionable schemes tend to be able to outsmart people, seemingly by sheer willpower. Not many people could pull off things like faking their death to defeat aliens, or one-upping a man while his brains have been scooped out - but when Xavier does, it's somehow completely unsurprising.