Jean Grey: The most powerful and complete Phoenix Force and host combination. Together they became the White Phoenix of the Crown. Death has stated that Jean is the rightful owner of the Phoenix Force and the embodiment of the Phoenix.
As Jean, her powers were constrained by psychic barriers, but when her power is fully manifested as Phoenix, she is the only Class 5 mutant alive, marking her as potentially the most powerful mutant to ever live. Telepathy: Phoenix has unlimited telepathic abilities that are only surpassed by her telekinesis.
One of the most powerful is the Phoenix Force. Tied directly to life and rebirth, the Phoenix Force gives its bearer godlike power that rivals that of any cosmic being but there's a cost, most Phoenix hosts go crazy. Another one of these powerful forces is the Power Cosmic.
In Jean Grey's form, it would become the White Phoenix of the Crown, with powers that outmatched the Dark Phoenix. Furthermore, the White Phoenix's powers had seemingly no upper power limit, as she could rewrite reality while miraculously controlling the Phoenix.
The White Phoenix of the Crow might just be the most powerful being in the Marvel Universe, even if she's still a mystery. The mythos of the Phoenix Force has evolved almost constantly ever since it debuted in Chris Claremont and Dave Cockrum's X-Men #101.
Jean Grey has been stated to be an Omega Level Mutant. She is also an Omega-Level Telepath. By birth, Jean is among the most powerful telepaths, telekinetic and psions. She is also one with the Phoenix Force, and while acting as its avatar she is one of the most powerful Abstract Entities in the Earth-616 universe.
Fully Phoenix powered cyclops was stronger than scarlet witch. It is obvious that white crown Phoenix is stronger.
The Phoenix Force is an immortal, indestructible, and mutable manifestation of the prime universal force of life. Born of the void between states of being, the Phoenix Force is a child of the universe.
There is a reason why Dark Phoenix was always an extinction-level threat as only a handful of cosmic entities are powerful enough to defeat her. Unfortunately, Scarlet Witch isn't one of them.
The Phoenix can't really be fought or defeated, but it looks like the Ghost Rider's attacks prove to be one of the cosmic entity's weaknesses. It's not enough to defeat it just yet, but it could turn out to be an important advantage over the Phoenix.
The Phoenix is destroyed when Jean is euthanized by Wolverine. The Dark Phoenix Saga is alluded to in X-Men: Apocalypse; in the final battle against Apocalypse, Professor X encourages Jean to use the full extent of her abilities to defeat Apocalypse.
Scarlet Witch has the ability to resist the Phoenix Force and can cause pain to its hosts. When Cyclops killed Professor X, he took on the persona of the Dark Phoenix, forcing Wanda and Hope Summers to join their powers and take him down.
Raven would win in a fight against Scarlet Witch because her extremely potent powers as an empath can abuse Wanda's greatest weakness, her own mind. Raven and Scarlet Witch are on more or less the same level of power, and both are capable of destruction on a near-cosmic level.
Jean Grey was the only Class Five mutant ever met by Charles Xavier (which implies Magneto and Pyro are Class Four), and her potential was stated to be limitless. It is unknown if Callisto counted herself and the Omega Gang as Class Three or less, or among the Class Four.
While we agree that Scarlet Witch has the ability to go all crazy with her powers, Phoenix Force can't be ignored at all. Jean Grey with her Phoenix Force, can easily win against Wanda. Her powers are great and Wanda just can't face the cosmic forces on that level.
1 Cyclops Has Always Known How To Beat Jean
In fact, just once comes to mind- Magneto and the Acolytes had taken mental control of the Blue Team and Storm and the Gold Team went to rescue them. Cyclops got the drop on Jean and hit her with a full power optic blast, taking her down.
Wanda Maximoff has never truly been defeated, only "losing" to the combined forces of Doctor Strange, Wong, and America Chavez after realizing the error in her ways. For a time, Wanda posed the greatest threat to the Multiverse, going on a violent rampage on Earth-838.
1. Arishem. One of the Celestials, Arishem the Judge is a being of such immense power that humans can only vaguely grasp what he's actually capable of. Arishem is so powerful that he created the Eternals, a race of beings that, in and of themselves, are also incredibly powerful.
Thor's immense strength, combat prowess, control over lightning, and enchanted hammer, Mjolnir, make him a formidable opponent against Scarlet Witch. In Avengers: Age of Ultron, he demonstrated his ability to resist her reality-warping powers and even physically overpower her.
Scarlet Witch
She has also defeated the Phoenix Force in battle. When the Phoenix took over Scott Summers, Wanda was able to not only eject the powerful entity from him but also undo the damage it has caused and cast the being out of the world by simply uttering, "No more Phoenix."
The Phoenix is among the most feared entities, having the power to cut and regrow existence and burn away "what doesn't work." Its power is usually channeled through hosts that the Phoenix bonds with, notably the mutant telepath Jean Grey whom the Phoenix has a particularly strong connection with.
Phoenix may be more experienced, but Raven had almost everything better. Trigon is much stronger then any of the other characters Jean defeated, and White Raven also had the ability to easily stop Jean's attacks.
Franklin Richards was omnipotent at some point, although his powers did not last forever. At the height of his powers, comic book Franklin Richards was much stronger than the MCU's Scarlet Witch ever was.
In Mark Waid's History of the Marvel Universe #3, Marvel has finally officially revealed who the most powerful mutant in the universe is. And no, it's not Wolverine, Jean Grey or Professor X. It's Marvel's Franklin Benjamin Richards.