Marvel Boy

John Grey is a mutant who attends Charles Xavier's school for gifted youngsters and serves as part of the X-Men as well as the Avengers. John was the first mutant born on Earth, his powers were so strong that the X-Gene activated the moment he was born, not needing any sort of genetic activation, similar to The Scarlet Witch. When Wanda Maximoff expanded the hex over the planet, his powers grew even stronger.

When John was sixteen years old, he was recruited by Charles Xavier to live in his home which served as a home for mutants who had been rejected by the world. Charles took on a fatherly role for John and trained him how to control his powers.

John also had a strong bond with Alpha the Eternity Warrior, as the two had been linked ever since John had been born in 2007. John fought alongside Alpha during the climax of the second Avengers civil war. When Alpha fled Earth following those events, John remained linked with Alpha and encouraged him to return to Earth to defeat Apocalypse who had taken over the Earth in the Avengers absence.

When the Phoenix Force split John's personalities, Alpha fought, and helped, John beat the Phoenix, it was also revealed that Alpha was John's real father. The two left Earth together so that John wouldn't be a danger to anyone anymore.

Early Life
John grew up as a fairly introverted child, finding it hard to interact with his peers due to anxiety caused by his abusive father. However, one day his mother reported his father and he was taken away, never to be seen again.

Following his father's arrest, John managed to open up to some peers and made friends in school. He was also very close to his mother.

The Decimation
During the Decimation; John began to fade away. He was panicked and his mother grabbed him, hugging him. All of a sudden, she began to fade while he came back. This left John on his own before being found by his aunt after a few hours.

The Blip
Following the Blip; John's aunt, who had raised him attempted to find John's mother, however, she never returned. John's aunt then killed herself, leaving John on his own once again. He then lived in his family apartment for several years, cutting himself off from everyone. For several years he emitted telepathic messages to Alpha the Eternity Warrior, who had been mentally linked with John ever since his birth.

Meeting Charles Xavier
Upon hearing John's cries of help, Charles set out to find him. Upon arriving at John's home, Charles was met with some telekinetic resistance from John, albeit, it was unintentional and out of fear as well as lack of control. Charles spoke to John on a telepathic plain which helped ease John's fears, John then decided to come with Charles so that he could learn to control his abilities.

Battle under Washington
During the invasion of Crayton Creed's base, John went with Billy, Charles and Ellie, all led by Logan to face Crayton. During the battle John fought the Sentinels as well as Polaris, he put up a good fight, although, Polaris defeated him.

When the Sentinels managed to corner the mutants out in open, John uses Charles and Ororo's distraction of speaking to Crayton to focus enough power to tear open the Sentinel's chest, which in turn, allowed Hank to through Logan at it, who impaled it and destroyed it. After Crayton's defeat, Charles attempted to help him but he refused, instead pulling a gun on Charles, who had turned his back, John noticed this and slowed the bullet as well as redirecting it. It ended up lodged in Charles spine, but Charles surived, Charles was then comatose for several weeks and when he awoke, was paralysed from the waist down. John was stressed about this but Charles told him not to worry.

Massacre at the Xavier Estate
Slaughter in New York

Personality
John is a very anxious boy who sometimes finds social interaction hard. He is shown to be very cautious when talking to people, even those he knows. He often doubts himself, even if he knows he is right.

John is a very kind and caring boy who enjoys making his friends happy, he can be sarcastic and cheeky which catches people off guard as they do not expect it from him.

When Entropy begins to manipulate John causing Dissociative Identity Disorder in John. With one of his personalities being extremely hostile and confident as well as blood thirsty due to his rage, while the real John is conflicted as he prefers to feel powerful but also does not like seeing people suffer.

Powers
John is a Class 5 Mutant on what is called the Essex scale. He is the only class 5 mutant, apart from Wanda Maximoff. However, he is significantly stronger than Wanda, albeit less in control.
 * Telekinesis - John can move objects with his mind. When Charles first encounters him, he cannot control it, however, after several years of training together, John quickly learns he can lift objects at will. The only downside is that the objects weight still matters and he can only lift an object if it is physically possible for a human to lift it. When John's mental blocks disappear and he can take full advantage of the Phoenix Force, he is able to lift objects ten times heavier than what he'd normally be able to lift.
 * Flight - John can hover, glide and walk on air. When he battled Apocalypse at Alpha's command, he walked on air as if it were solid before hovering in the air while he unleashed his power.
 * Molecular Manipulation - At a full extent of her power, he can manipulate matter at a molecular level at will, with the exception of adamantium or Vibranium, or anything encased or bonded with the two metals.
 * Disintegration - John is able to atomize nearly anything within his surroundings at will when at the full extent of his powers.
 * Telepathy - John has the ability to read, communicate with, and control other people's minds, similar to Charles Xavier, although initially to a lesser extent. When John first meets Charles, Xavier offers John lessons on how to amplify and control his power. During these lessons, Charles, Hank McCoy and Nathan Essex study him and develop ways to numb John's connection if need be. During Apocalypse's last stand; John comes to the aid of Alpha the Eternity warrior who encourages him to unleash his power. Charles realises this will break the numbing on John's powers and attempts to call on Essex to stop John. However, it is too late and John defeats Apocalypse, but, at the same time destroys the numbing, restoring all memories and power. Once the blocks were destroyed, he far exceeded his mentor's abilities, being able to transcend great distances and even defend his own mind from other telepaths.
 * Energy Absorption - John is shown to be able to merge with and absorb different forms of energy, including the Phoenix Force, which he begins merging with at 11 years old, as soon as his mutant gene is activated. John isn't shown to be able to control this power and it seems to happen at random times, whether he wants it to or not; similar to Rouge's power.
 * Phoenix Force Manipulation -

Equipment

 * Cerebro - When working with Charles on controlling his power, John was allowed to use Cerebro. Although this was mainly so than Hank and Nathan could study John.
 * X-Jet - John used his telepathy to learn from Charles how to fly the X-Jet which Charles disproves of.

Facilities

 * Charles Xavier's School for Gifted Youngsters - Base of Operations

Family

 * Alpha - Father/Former Situational Enemy
 * Jean Grey† - Mother
 * Aran Grey - Adoptive Father/Former Abuser
 * Elaine† - Aunt
 * Charles Xavier/Professor X - Adoptive Father/Professor/Former Situational Enemy

Allies

 * Charles Xavier's School for Gifted Youngsters
 * Sophie Summers/Cyclops - Girlfriend
 * Robert Drake/Iceman
 * William Maximoff/Wiccan - Best friend
 * Tommy Maximoff/Speed
 * Kitty Pride/Shadowcat
 * Jubilation Lee/Jubilee
 * X-Men
 * Wanda Maximoff/Scarlet Witch
 * Logan/Wolverine
 * Ellie Braddock/Pyslocke
 * Ororo Munro/Storm
 * Hank McCoy/Beast
 * Wade Wilson/Deadpool

Enemies

 * The Brotherhood of Mutants
 * Erik Lehnsherr/Magneto - Former Ally
 * Marie Harper/Rouge - Former Ally
 * Alex Summers/Havok - Former Ally
 * Remy LeBeau/Gambit

Trivia

 * With Six appearances to date; Marvel Boy has the second most appearance of the X-Men to date.
 * Scarlet Witch has ten appearances in the MCU.
 * John is the first mentally challenged character in the MCU.
 * John has anxiety which is shown when interacting with others, especially those he does not know.
 * John is also shown to have Dissociative Identity Disorder which causes him to become even more dangerous as he allows his more dangerous persona, who is known as Phoenix, to take control.
 * John Grey/Marvel Boy is confirmed to be the most powerful character in the Marvel Cinematic Universe beating out Captain Marvel, Thor, Scarlet Witch as well as the Eternity and Infinity Warriors.
 * John is one of many gender swapped characters in the Marvel Cinematic Universe.
 * Among others are The Ancient One, Ajak, Makarri and Sophie Summers/Cyclops.