It's Not Always Good To Be Special|X-Men

S1 E10:Xavier

Mental Link: Charles had the ability to develop a mental link with any person which remains as a connection to that individual. This was shown when Jean Grey linked with him to communicate with the others in the X-Jet before perishing. Charles uses this power to project his mind into the future by linking the future Wolverine's mind and use them as a bridge to it where he is able to connect to and converse with his future self.
Mnemokinesis: Charles could manipulate the memories individuals. Xavier can erase, restore, or even implant false memories into a person's mind. He once threatened Wolverine by telling him that he could make him believe he was a six-year-old girl. Also, aside from erasing memories, Charles has the ability to restore memories as well. The latter was demonstrated when he restored the memories of Moira MacTaggert, which he had initially erased, causing her to remember all the time she spent with him.
Amnesia Inducement: Charles had the ability to cause loss of particular memories and amnesia in another person or group of people. Here, he used this power while passionately kissing the beautiful Moira MacTaggert and makes her forget all the time that she spent with Xavier and the mutants (although she recalls fragments, including the kiss). This might have been used to save himself and made it look like Jean killed him.
Illusion Projection: Charles was able to generate realistic illusions. Charles could make himself and others invisible to others. Professor X uses this power to convince Mystique to not kill Bolivar Trask. His illusions took the form of himself, but able to stand. Any damages he had on his body would appear on his projection. His illusion based projection allowed him to perceive events from afar with only his projection being present.
Psychic Barrier Generation: Charles was able to put mental blocks in Jean Grey's mind so she couldn't unlock the Phoenix part of her personality.
Pain Inducement: When his powers were boosted by Cerebro, Charles had enough power to cause every mutant in the world to experience a lethal, excruciating pain. He was also able to make every human experience the same lethal pain when Magneto reversed Cerebro. These blasts could not effect Magneto, as he was wearing his helmet. When his powers were out of control due to mental illness, Charles would release psychic pulses that could effect hundreds of people across over a mile radius. They paralyzed and tortured all those effected, and could have killed anyone who was forced to experience it for more then a few minutes.
Psychic Immunity: According to William Stryker, the mind control serum will have no effect on Xavier, as his resistance to other people's telepathy make it very difficult to control him. He can resist psychic attacks from others and protect his allies. It is likely Emma Frost could not telepathically attack Xavier or Erik as Xavier defended both their minds from her, though he did feel a slight sting from her when trying to read her mind.
America's most wanted octogenarian."
"I'm a nonagenarian, actually.
DONALD PIERCE AND PROFESSOR X
Longevity: Professor X lived a very long life, and he was very youthful as he did not visibly age between 1962 and 1992, along with Magneto, Mystique, Beast, and Havok. It is unknown how long he would have continued to live if not for his premature death at the hands of X-24.

Next to him was Jean grey arguably the most powerful telepath.

Jean Grey is an extremely powerful mutant (the only known Class 5 mutant in the original timeline) whose abilities varied across her appearances. From a burgeoning psychic whose abilities were contained until she could gain better control of them, Jean's powers evolved immensely due to her near-death experience in the original timeline and from letting go of her inhibitions and merging with the Phoenix Force in the revised timeline.

In the original timeline, her eyes display a fiery glow and her body manifests what appears to be flames when exerting her powers. Upon her revival, Jean's eyes and veins darken and her hair becomes akin to fire when she uses her powers.

In the revised timeline, when unleashing the full extent of her powers, Jean's powers manifested around her as a fiery raptor. Her powers is vastly amplified after merging with the Phoenix, allowing her to accomplish feats impossible if attempted alone. Her power signature is seen as glowing fiery veins across her skin and her clothes as well as her immediate environment atomizing and repairing themselves, reflecting the sheer volatile power of the energy within her.
Telekinesis: Jean has the ability to move objects with her mind, ranging from doors to people, cars and even trains. Beast once stated that Jean's powers had no limits. Her telekinetic abilities, when exerted to their full potential, are so acute that she can dismantle a gun piece by piece in the original timeline. In the revised timeline, she can sustain multiple telekinetic feats at once and even intercept Quicksilver while he is running at superhuman speeds when merged with the Phoenix. Even without the Phoenix, her telekinetic control allowed her to assist Magneto in rebuilding the X-Mansion after the events of Apocalypse, rebuilding the school alongside Erik piece by piece.
Flight: Jean can fly using her telekinesis by project herself through the air, moreso displayed in the revised timeline. During the battle against Apocalypse, Jean was able to walk on and float in the air while attacking him. When merged with the Phoenix, she is able to simulate self-propelled flight at considerable speeds. She is even able to easily soar through outer space and the upper atmosphere.