As if there weren't enough Marvel-named characters, Jean Grey originally joined the X-Men under the name Marvel Girl. Her only power was telekinesis — when she later showed telepathic skills, it was "revealed" (i.e., retconned) that Professor X had suppressed them when she was a teen in training.

While they fought battles and became known worldwide as the X-Men, team member Angel (the one with the wings) crushed on Jean hard, while Jean liked Cyclops, but was too shy to say anything. She DID invite Cyclops on her date with Angel, not at all awkward!

Because Cyclops was paranoid he'd hurt those near him, he initially pushed Jean away, but eventually they got together and became the X-Power Couple.

When Xavier recruited a class of new students, the OG X-Men took a break and Jean became... a swimsuit model?! I mean, Cyclops became a radio announcer, which makes about as much sense.

Just before alien race the Z'Nox tried taking over Earth, Professor X decided to take a sabbatical, telling no one but Jean and having shape-shifting (and dying) mutant Changeling take his place. Why only tell Jean? Well, with Xavier physically gone, he'd no longer be able to control the psychic blocks he'd put in Jean's head since childhood, and thought she might want to prepare for the sudden onslaught of 10 times the telepathic powers. Surprisingly, she's able to handle it!

Sensing an enormous mutant power in the Pacific, Professor X (the real deal) sends the team out to investigate. They're all snagged by living island and enormous mutant Krakoa, who feeds off their energy. Two rescue teams later, Xavier forms the New X-Men to help, and they finally destroy Krakoa.

With a whole new crew around, 13 members seems too many, and all the original X-Men but Cyclops decide to take a break from battling. Jean still pals around with Storm and goes on cute dates with Scott.

The X-Men reunite for Christmas sightseeing in Manhattan when they're attacked by Sentinels, robots designed by mutant-hater Stephen Lang. Jean and others are kidnapped and, according to friend of Xavier, boating enthusiast, and solar flare expert Dr. Peter Corbeau, probably taken into outer space.

Under cover of examining solar activity, Dr. Corbeau flies his research ship StarCore out to rescue Jean and the other captured X-Men. Unfortunately for him, right after he blasts off, there actually is massive solar activity detected. Whoops.

The whole gang's back together again! Unfortunately it's on Lang's space station, with all the escape pods already taken by Lang's anti-mutant minions, and there's a massive, life-destroying solar flare headed their way. Hmm. They can take Corbeau's shuttle, since its core is shielded to protect those inside from radiation, but the autopilot's busted — someone has to manually pilot the ship back to Earth in the cockpit, exposing themselves to massive radiation. Guess who volunteers.

To be fair, Jean's immense telekinetic powers allow her to pilot the complex ship solo and give her the best chance out of everyone to shield herself from the radiation. Unfortunately the massive flare pushes her powers to the ultimate limit, and as she's overcome she sends out a psychic scream heard 'round the universe.

The ship crash lands in the ocean, and Jean, presumed dead, rises from the wreckage and declares she's no longer Jean Grey, she's The Phoenix, Power Incarnate and Life Itself. OK, that's nice, but the cops are coming and the X-Men have to beat feet.

At first Phoenix does fine as an X-Man, excelling even. During a power grab by the Emperor of the alien Shi'ar empire, she manages to repair the M'Kraan Crystal, aka the Nexus Of All Reality, thus stopping the entire universe from collapsing into nothingness. The Emperor's sister Lilandra, who'd called the X-Men in to help, points out that while it's great reality still exists, power that immense in one person is probably gonna cause trouble down the line.

Some time later, believing the rest of the X-Men dead in a battle, Jean/Phoenix decides to take a sad vacation on Muir Island. She's taken in by a powerful psychic illusion set up by Jason Wyngarde and Emma Frost (aka the White Queen), members of the villainous (and vaguely Victorian) Hellfire Club. They convince her she's dreamt her entire life with the X-Men, and she's really Hellfire member The Black Queen, set to wed Wyngarde. Also that she's always worn a way sexier and more evil costume.

When the X-Men attempt to rescue Jean/Phoenix from the Hellfire club, she turns against and easily captures them. Only Cyclop's psychic love connection (yeesh) breaks through the illusion Jean's trapped in, letting him into her mind, where he battles Wyndham and seems to die doing so. That breaks the illusion completely... but also breaks down Jean's mental barriers. The full Phoenix Force comes out, and as the X-Men escape, Jean transforms into Dark Phoenix, tears their ship apart, and zips off to the depths of space.

Dark Phoenix flies halfway across the universe and exhausted, decides to eat a sun which goes nova. Unfortunately that kills an entire solar system's worth of intelligent beings. Lilandra and other members of Shi'ar/Kree/Skrull rule decide for the good of the universe, Dark Phoenix must face punishment and be destroyed.

Though she murdered billions of people, the X-Men decide that Jean's still one of their own and that they're going to rescue her, resulting in a wildly one-sided battle where scores of alien warriors easily overpower the X-Men.

The Phoenix is momentarily weakened when she psychically feels the pain of her teammates, and is seemingly destroyed when Lilandra blasts her with an immensely powerful beam.

This particular twist comes around much later, when a new batch of X-Men comic writers wanted to bring back the Phoenix but wanted to get around the, y'know, genocide. Turns out that what killed all those people was a copy of Jean Grey's body made by the Phoenix Force, which grew more corrupt the further away it moved from Jean's real body... which was found by the Avengers to be at the bottom of the Hudson river this whole time. Phoenix is BACK, baby!

Scott marries a Jean Grey clone, their baby is kidnapped and comes back as ultrabuff techno-infected future-son Cable, the clone makes a deal with some demons, Real Jean's just hanging around during all this and, on killing her clone, gets a piece of her soul back along with her memories... and it goes on like this!

The Dark Phoenix saga's still unwinding in the world of comics, but her basic origin story and ultimate downfall at the hands of her own teammates is captured in Dark Phoenix, hopefully minus some of the melodramatic twists. Otherwise, the film would be six hours long.