Jean Grey
At the age of 10, Jean Grey's telepathic powers brought her to the attention of Professor Charles Xavier, leader of the X-Men. Her potential was immediately evident and she became a trainee in the fledgling group of mutant superheroes. Her telepathic powers were so great that Xavier blocked them until she was mature enough to keep them under control. Jean Grey's powers grew immensely in her later incarnation as Phoenix, when she became arguably the most powerful figure in the Marvel universe.
Ms. Marvel
Ms. Marvel, also known as Carol Danvers, gained her powers through a combination of alien and human genes. Her original incarnation displayed superhuman powers such as incredible strength, stamina and the ability to fly. After an encounter with a second alien race, Ms. Marvel gained the ability to draw upon the power of a white hole in space, greatly increasing her strength.
Storm
Another long-standing member of the X-Men, Storm's primary power is her ability to control the weather. She also possesses magical abilities and a strong command of combat strategy. Storm is considered a potential Omega-level mutant within the X-Men universe. The few confirmed Omega-level mutants, such as Jean Grey, are among the most powerful Marvel superheroes.
Rachel Grey
Rachel Grey, also known as Rachel Anne Summers, is the daughter of Jean Grey and mutant Scott Summers, albeit versions from an alternate future. She inherited many of her mother's powers, making her a particularly formidable character. Her powers include telekinetic, telepathic and limited time-altering abilities. Unlike her mother, she is not a confirmed Omega-level mutant.
Rogue
Rogue's ability to absorb the powers of other mutant superheroes gives her an almost endless opportunity for advancement. She started out as a criminal character, a role that led to an early confrontation with Ms. Marvel, whose powers she absorbed. Rejecting her criminal life, Rogue joined the X-Men. Her ability to absorb powers makes her a changeable, yet very powerful, character.
Scarlet Witch
The Scarlet Witch, also known as Wanda Magnus, is a powerful Marvel character due to her unique core ability. Her super power is unlike any other as she can alter probability to cause mishaps for her foes, says Don Markstein's Toonopedia website. By placing a hex upon her foes, the Scarlet Witch can severely limit the success of her opponents. She has appeared in various comics, including the X-Men and Avengers.