Mastered Ultra Instinct 4, is a form that combines the power of Mastered Ultra Instinct with the fourth Super Saiyan form.
This form can be accessed by absorbing the powers of a ultra instinct, activating them and then transforming into a Super Saiyan 4, or through vigorous ki control by absorbing a spirt bomb with godly ki as a SSJ 4 and then obtaining that Godly ki for oneself, as seen with Goku in the Super anime. This form exceedingly surpasses all of its predecessor.
A Mastered Ultra Instinct 4's hair grows to the length of a Super Saiyan 3's hair, except white. The fur on their chest also turns white as well. Other than this and a white aura, it looks like a white haired Super Saiyan 3 Super Saiyan 4. Their muscles are also really large, too.
The original user of the Mastered Ultra Instinct 4. He is the first to use it, the first to master it, and generally the first to obtain new forms of each stage of Super Saiyan. It is safe to say that Goku is the master of the Super Saiyan.
Usage & Power
Saiyan Physiology: When Goku was the Master of Ultra Instinct 4, he was the living embodiment of the Saiyan Race, making him one of the most powerful beings in existence. When using his Spirit Bomb in this form it's enough might to destroy entire planets and was universally known as the Saiyan-God  before separating from the it after killing Frieza.
- Superhuman Strength: This form can single-handedly defeated the entire Ginyu Force, and was able to defeat the powerful Dark Emperor Frieza in battle.
- Superhuman Durability: They were strong enough to withstand the force of Frieza's Darkness Eye Beam, as well as several of his punches.
- Flight: They have the power to fly and hover in the air.
- Energy Absorption: They can absorb and consume the ki of living beings and entire universes. 
- Anti-Matter Blast: They can fire beams of concentrated anti-matter energy from their hands.
- Light Manipulation: they can use the transformation to manipulate the light cast by humanoid beings to give them life and use them as loyal servants to aid they in battle.
- Near limitless cosmic powers;
- Matter and energy manipulation
- Reality warping
- Absorption of entire universes
In this state, Goku's power massively increases to godly levels far exceeding the Gods of Destruction, making him the strongest he has ever been in history, ranking as among the most powerful entities in the multiverse.
The intensity of Ultra Instinct Goku's power was so great that his shirt was completely shredded when activated. In addition to this form's vast levels of power, it retains its unique effect on Goku's Saiyan Power ability, allowing his speed, power, general efficiency, and ki to increase as he continues to fight an equally or even more powerful opponent, but to a significant degree. Its most notable trait is that it grants Goku complete mastery over Ultra Instinct, making all of his moves automatic and able to both defend and counterattack with ease without being hindered by the thoughts that previously made Goku's use of Ultra Instinct imperfect. It was not until Goku let go of all of his doubts and live in the moment to fully understand Whis' teachings; thus allowing him to access the full potential of his fighting ability. Despite being a form of acts on neutral impulse, it can still channel his rage to amplify its power to staggering new levels, as shown when Goku's initial stalemate against the limit-breaking Jirenbecame a crushing assault that quickly pummeled Jiren into submission after Goku's fury at Jiren's shameless attack of the spectators. He also displayed such vast Ki control that he could calmly repel and contain any energy assault thrown at him.
In spite of the form's incredible levels of power, it has its faults. Similar to the reckless over-usage of Kaio-ken, the user can only sustain the sheer power of the form for a minute or so before their body breaks down from pushing so far beyond their natural limits. The time limit ending is shown from blood rupturing from the user's body as well as dark ki electrical shocks that will cause them severe pain and eventually force them into unconsciousness. In more severe cases, Whis noted it could potentially kill the user. It has also been strongly implied in Xenoverse 2 and Super, via comments made by Whis, that the drawback of this form is the high cost of stamina. This is similar with the Ultra Instinct -Sign- form, whereafter Goku had reverted to his base form, he was depleted of his energy to the point of severe fatigue, struggled to move, and clutched at his chest after defeating Kefla.
Moreover, Goku apparently attained Ultra Instinct purely by accident, as when he was confronted by Vegeta about not using it during their rematch in Gizard Wasteland, Goku replied that he is unable to tap into its power at will, meaning that the form can only appear if Goku is in extreme danger. This is supported by the encounter of Ultra Instinct in Xenoverse 2, where the Future Warrior battled Goku, who only managed to unleash the form after being under extreme stress from his opponent's attacks.
- Goku in this form in the main dragonball canon makes him the 3rd strongest character in the dragonball universe after the Grand Priest and Zeno the same thing can't be said about about the Dragon Ball fanon though also even though Goku in this form has more power then most angels like Whis and Vados the only thing that is not more powerful is his strength and endurance compared to the angels
- The Damage received from maintaining this form is The same as regular Mastered Ultra Instinct because Goku does not receive any pain from Transforming into Super Saiyan 4 because all this form is, is SSJ4 added on to Mastered Ultra Instinct