PROFESSOR X

Xavier's original body was crippled after his legs were crushed by Lucifer, as reported in X-Men (1st series) #9. After being overrun by a Brood Queen embryo, the professor's consciousness was transfered into a younger, fully operational body in Uncanny X-Men #167. This body was later crippled by the Shadow King in Uncanny X-Men #280.

Xavier was "possessed" by Onslaught from X-Men (2nd series) #25 until Uncanny X-Men (1st series) #336. He lost his telepathy for a time as a result, but it returned in X-Men (2nd series) #84.

Professor X seemingly regained the ability to walk in New X-Men (1st series) #126, but it was revealed as a trick caused by Xorn and nano-Sentinels in #146. He genuinely regained the use of his legs after M-Day, as reported in X-Men: Deadly Genesis #5-6, but also lost his telepathy. His powers were restored after exposure to the M'Kraan crystal in Uncanny #485-486.

Xavier was killed by Cyclops in Avengers vs. X-Men #11 while Scott was under the influence of a Dark Phoenix manifestation. Traces of his consciousness allegedly remained inside his telepathic brain, which was surgically purloined by the Red Skull in three volumes of Uncanny Avengers. His full psyche was maintained on the astral plane by his enemy, the Shadow King, who sought to torture his eternal foe. Eventually, Xavier convinced Fantomex to trade places with him on the astral plane, allowing Xavier to rewrite the nano-technology in Fantomex's body to make it a young duplicate of his original form, reborn in corporeal form as "X" in Astonishing X-Men (4th series) #6-7.