With the Phoenix Force, Jean Grey is an Omega level mutant, meaning there is simply no limit to what she can accomplish, and though the Scarlet Witch would certainly put up a strong, mind-bending fight, Jean Grey would likely take the victory during this huge battle.
The Helmet of Nabu gives Doctor Fate great power. In many ways, he's easily Jean's superior, but the mutant has always been good at taking down enemies that are stronger than her.
In the main Marvel Comics continuity, despite all her power, the Scarlet Witch could not stand next to god-like forces such as the Phoenix Force, Galactus, and the Living Tribunal.
Therefore, by the end of the Infinity Saga, Captain Marvel was likely stronger than Wanda, all things considered. However, after discovering the true nature of her powers in WandaVision and accessing the Darkhold magic in Doctor Strange 2, Scarlet Witch is now more powerful than Captain Marvel.
With the Phoenix Force, Jean Grey is an Omega level mutant, meaning there is simply no limit to what she can accomplish, and though the Scarlet Witch would certainly put up a strong, mind-bending fight, Jean Grey would likely take the victory during this huge battle.
Wanda is famous for her “no more mutants” feat where she wiped out a majority of mutantkind after making a world where mutants were the majority of the world population. In the MCU, Scarlet Witch may put up a good fight, but Thor wins majority if not all of the fights.
Professor X was always able to beat her in psychic combat, using his immense power to shut down his student. While he's not always the best person and has been wrong a lot, his powers and skills make him one of the most formidable psychic combatants ever.
Jean, though, is one of the most powerful telepaths on the planet and would be able to shut his mind down without too much fuss. It might take her a little bit but her telekinesis would let her protect herself long enough to put the Hulk down.
In What If...? #27 (by Mary Jo Duffy, Jerry Bingham, John Stuart, Carl Garford, and Simek Chaing), the Jean Grey of a timeline where she didn't perish during the "Dark Phoenix Saga" ended up proving that she could fight Galactus and Terrax all on her own.
Although he is an extremely skilled marksman, Clint Barton is often considered to be the weakest member of the team seeing as he's just a regular guy with a bow and arrow. That certainly means that Hawkeye one of the weakest Avengers.
Her full potential was not showcased until WandaVision. Scarlet Witch was by far the most powerful MCU Phase 4 character, yet Wanda could not beat Thanos in either Avengers: Infinity War or Avengers: Endgame.
Rogue is one of the X-Men's most formidable members. Her mutant ability to absorb the powers of others makes her a great powerhouse, as she can have the powers of anyone she touches. This ability has become even more potent since she mastered it, and it was also how she was able to kill Scarlet Witch.
Jean Grey is one of the most powerful telepaths on Earth. Her powerful telekinesis makes her one of the most dangerous heroes around. She can't match Shazam's physical might, but her telekinetic abilities allow her to hit way above her weight class and protect herself from devastating attacks.
If Thanos does not possess any of the Stones, the Phoenix Force would be too much for him to battle against. Despite his experience, his weapons, his tactics, his willpower or even his armies, the Phoenix can wipe through all of this because of the raw power that is at her disposal.
Wanda ceased to be a mutant in Earth-616 in a controversial Marvel Comics retcon, but in this reality, she was considered an Omega-Level Mutant capable of telekinesis, telepathy, and more.
Even without the Phoenix force, it's arguable that Jean could destroy Wolverine. After all, much like Xavier, she can enter his mind and manipulate it in such a way that he could go insane.
It really depends on the situation. Wanda has command over Chaos Magic on a consistent basis, thanks to the link she has with an old God of Chaos named Chthon. Meanwhile, Jean can only do so much on her own as a telepath. She may be Omega-level, but all that power often puts a strain on her body.
As her powers likely come at least in part from the Mind Stone inside of Loki's scepter, Wanda's abilities include telekinesis, energy manipulation, and some form of neuroelectric interfacing that allows her to both read thoughts and also give her targets waking nightmares.
Weaknesses. Initially, Jean's limited power made her vulnerable to a variety of skilled and/or powerful opponents. Dissociative Identity Disorder: As "Phoenix", her main vulnerability was that if she became emotionally unstable, she would lose control of her powers.
Deadpool is pretty weak against mutants like Jean Grey as it is. Pitching him against a godly force like the Phoenix is leading to disaster. The Phoenix Force comprehends existence, time, and space on a level that Deadpool just doesn't operate on.
In the MCU, Loki is clearly more powerful. Wanda can only project her astral form into other branches, but Loki is maintaining all branches at once. He's returned the multiverse to its true original form of the world-tree Yggdrassil. Not just maintaining them, but can likely kill off branches at will.
A stealthy application of Scarlet Witch's magic could take down a Hulk, but if they realize what she's up to, their emotional reaction is likely to be enough to give them a chance to stop her.
If it came down to it and Odin saw Scarlett Witch as a threat to the Universe and Multiverse and decided to try and take her down, who would win? Odin.
