Jean Grey Vs. Scarlet Witch: Who Would Win?
You may have noticed that in "Spider-Man: Brand New Day," Jean Grey (Sadie Sink) goes through an antagonist arc that's presented in a very similar way as that of Wanda "Scarlet Witch" Maximoff (Elizabeth Olsen) on "WandaVision" and in "Doctor Strange in the Multiverse of Madness." If you haven't, Looper has an entire article on how "Brand New Day" recycles the powerful villain story of Scarlet Witch by infusing Jean with similar qualities and even powers.
Though Wanda's apparent death after the events of "Multiverse of Madness" means that the MCU incarnations of the pair might not meet any time soon, their similarity raises an interesting question. Both characters have displayed some serious power over the course of their comic book and movie histories, so the battle between them would no doubt be brutal. But which of the two characters would come out on top, should they ever clash? On the red corner, we have Jean Grey. On the ... other red corner, we have the Scarlet Witch. Who would win in a fight?
Both characters are powerful in their own ways
In the comics, Jean Grey is arguably the strongest Omega-level mutant and an absurdly powerful telepath, empath, and telekinetic. She can do virtually anything with these powers, up to and including reality manipulation and effective immortality by way of transferring her consciousness into another living being.
The MCU version of Jean starts out weaker. Her primary power is possessing people within a 33-foot radius. Sure, this makes her a menace who can chain her jumps seemingly infinitely and possess powerful individuals. Still, both Spider-Man (Tom Holland) and Bill Metzger (Tramell Tillman) manage to temporarily restrain her abilities with sufficient isolation. Toward the end of "Spider-Man: Brand New Day," a powered-up Jean displays strong telekinesis, as well as the ability to create a large psionic bubble and control the vast number of people trapped within it.
The comic book version of Wanda Maximoff is a step above even Jean. The untold truth of the Scarlet Witch is complicated to say the least, but in a nutshell, Wanda is the Earth-616 timeline's "nexus being" — effectively the personified force of this universe. She can't be permanently killed and she's able to shape reality as she likes, up to and including the infamous M-Day Decimation event where she temporarily depowers nearly all of Earth's mutants simply by wishing it.
The MCU Scarlet Witch also wields vast power. Apart from telekinetic and mental abilities that are somewhat on par with what the MCU Jean has displayed, she's an unparalleled chaos magician who can rewrite reality to the point of creating life. In "Doctor Strange in the Multiverse of Madness," she handily fights and wins the combined might of Kamar-Taj wizards while under the influence of the Darkhold. Even before unlocking her full abilities, she's a powerhouse: As seen on "WandaVision," she can create a Hex bubble, inside which she's virtually omnipotent.
Wanda would probably come out on top, unless the Phoenix Force comes out to play
Looking at the pair's power levels, it's clear that Jean is no slouch. However, the comic book Wanda's more loosely-defined power set that combines magical spells with innate reality-bending abilities is a touch above anything that any version of baseline Jean can bring to the table. Apart from her vast offensive and defensive powers, the Scarlet Witch's sheer unkillability and status as the Earth-616 nexus being give her an edge.
In the MCU, things might be more interesting. While Wanda would probably make short work of the bodyhopper version of Jean, the mutant's late-game powers show great telekinetic talent and an unprecedented level of control over a large number of people. Wanda is more experienced and has far more feats due to her lengthier MCU tenure, but the sheer immensity of Jean's telepathic powers might make it a surprisingly even fight.
However, the rulebook flies out of the window if any version of Wanda is facing a Jean who's hosting the Phoenix Force. While the Earth-616 Wanda might be the nexus being of her universe, the Phoenix is a completely indestructible nexus of the entire multiverse's psionic energy — think the Big Bang, the end of everything, and much of what happens in between, all rolled into one big fiery bird. Apart from its obvious and rather literal firepower, the Phoenix Force can manipulate time, reality, all forms of energy, and the very fabric of existence as it pleases. As such, there really isn't a lot that even the Scarlet Witch can do if it decides to step in the ring with her.