Professor Charles Xavier was an Alpha-Level Mutant,an Omega Class Telepath, was said to possess the most powerful brain in existence, to be the world's greatest telepath and possesses vast psionic powers:

Telepathy: Able to read minds and project his own thoughts into the minds of others within a radius of 250 miles (on Earth). With extreme effort he can greatly extend that radius. When synched withCerebro or Cerebra, he can connect to every mind on a planet. After he was thrown into the M'Kraan Crystal, it not only restored his mutation, but made his telepathy more powerful than it has been previously, thereby making him the world's most powerful telepath once again.

Telepathic Illusion: ability to create realistic telepathic illusions and cause people to experience events which are not actually occurring.

Telepathic Cloak: can mask his presence from being detected by others. His abilities can at times go undetected or be counteracted by other more powerful telepaths depending on their level of skill in using their own psi abilities. He can extend these defenses to others around him as well.

Mind Link: ability to develop a mental link with any person which remains as a connection to that individual...