Marvel Girl, Phoenix. Founding member of the X-Men, founding member of X-Factor, founding member of the Krakoan Quiet Council. Leader of X-Men Red. It's hard to separate modern mutant history from the history of Jean Grey, she is as central a character in the tale of mutantkind as anyone outside Charles Xavier himself. She has been in the superhero business since she was a teenager, and has saved the galaxy and the planet more times than she will ever get credit for.
Most of humanity and metahumanity knows her as just that, Jean Grey, paragon of the heroic mutant, a figure that stands for love and compassion. Others might know her as the strongest telepath on the planet, and likely one of the strongest in the universe, an Omega level mutant; a mutant whose primary power has reached a limitless, undefinable upper limit, allowing them to possess world-altering or multiversal capabilities.
She is nearly as strong a telekinetic, making short work of physical based combatants with just the psychic power of her mind alone. When opponents strategize against mutantkind, and the X-Men, Jean Grey is one of, if not the, very first individual threats analyzed and schemed for. Not that any of the schemes have yet to neutralize her for long, let alone for good.
Fewer on Earth, but more among the cosmos, know Jean Grey as the host of the Phoenix Force, and the once dreaded Dark Phoenix, an embodiment of either the life force of the omni-verse, or the embodiment of destruction and chaos in the universe. Some theorize that she is, for all intents and purposes, immortal because of her connection to the Phoenix Force.
Still more claim she is still a cosmic godling, just disguised as a regular mutant in order to live a so-called 'normal' life on the planet for as long as her loved ones live. Whatever the truth of it, she is currently both a member of the Quiet Council, and a member of the X-Men, based in the Krakoan Treehouse on Manhattan Island. Friend and ally to any hero, Jean has spent much of recent history getting closer to her family and navigating Krakoan politics.