Season 6 of My Hero Academia has been stellar, as fans have seen what an all-out war between the Heroes and Villains would look like. Had All Might still been active, there is a good chance that the Pro Heroes would have suffered far fewer losses. All Might was the No.1 Pro Hero in Japan for well over a decade, and he held that position thanks to One For All.
This Quirk gave All Might superhuman strength, speed, reflexes, endurance, and durability. It can give the user other Quirks as well, but All Might was only able to use its superhuman physical traits. Before he was permanently injured, All Might was in his prime and virtually unbeatable, but there are a few characters who still could have defeated him.
10 Tomura Can End All Might With A Touch
Tomura was not always a villain. In fact, it was his father who started him down that path by being abusive. He awakened the Decay Quirk when he was a child, and he ended up killing his entire family because he could not control it.
Decay allows him to disintegrate anything that he touches with his fingers. This power has gotten much stronger, to the point that it can disintegrate anything within a city-wide area. Prime All Might may have been close to unbeatable thanks to his durability, but even his body would not survive complete disintegration.
9 Eri Can Erase People From Existence
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Eri is an adorable and fun-loving little girl, and she has one of the most overpowered Quirks in MHA. It is called Rewind, and it allows her to revert someone back to a previous state. This power is great for healing, but it can also do serious damage.
She can revert someone back to a time when they did not have their Quirk, which means that All Might would return to being a Quirkless human. Rewind can even revert someone to a time when they were not even born yet, which means that she could essentially erase prime All Might from existence.
8 Hitoshi Shinso Can Force Him To Obey His Commands
Hitoshi Shinso was ashamed of his Quirk because it is the kind of power that Villains would use. It is called Brainwashing, and as its name suggests, his targets are forced to obey his commands. In order for the Quirk to activate, the target must verbally respond to him.
Those affected cannot carry out tasks that require advanced brain functions, but he can force his opponent to stop moving, thus ending the fight immediately. Even prime All Might would fall victim to this power if he spoke at the wrong time.
7 Gigantomachia Is Virtually Unstoppable
Of all the Villains, Gigantomachia really stands out because of his loyalty and selflessness. He is All For One's most devout servant, and he serves as his personal bodyguard. His full strength was shown during Season 6, where he destroyed several towns and plowed through multiple Heroes at once.
Other than his size, Machia has a Quirk which blocks all pain, and another which hardens the muscles in his body. Together, these Quirks would allow him to withstand prime All Might's attacks, and his massive claws would be able to deal damage to All Might's body.
6 Endeavor Could Burn All Might To Ash
Endeavor spent years trying to surpass All Might, to the point that he was willing to ruin his entire family. Oddly enough, he could have actually used his Quirk to beat All Might at any time. With Hellflame, he can produce and manipulate large quantities of fire.
These flames are extremely powerful, and they can easily turn someone into ash. It is true that All Might's body was incredibly durable, especially during his prime, but even his body could not withstand such immense heat for long.
5 Midnight Can Put Him To Sleep
Many of the students at U.A. High School liked Midnight, which is why her death was so sad. In terms of combat ability, All Might would destroy her. In fact, he would not even need to be in his prime to do so. Luckily, her Somnambulist Quirk gives her an edge.
It allows her body to produce a special aroma that puts people to sleep, and it has been shown to work better on men. As a man, this puts All Might at a huge disadvantage, because as strong as he was in his prime, he still needs to be awake to actually fight.
4 Mr. Compress Can Turn All Might Into A Marble
Thanks to his Quirk, Mr. Compress was able to become a master thief wanted throughout Japan. Compress allows him to compress anything he touches into a marble-like object, including people, and they will remain in such a state until he releases them.
Even with all his power, prime All Might cannot stop himself from being transformed. This power can also be used on individual body parts, which means that Compress could maim All Might by removing one or more limbs. Without a healing factor, All Might would never be able to regain those limbs.
3 Thirteen Can Disintegrate Anything With Black Hole
Thirteen is a Pro Hero who specializes in search and rescue operations, but when push comes to shove, she can fight. She possesses the Black Hole Quirk, which gives her hands the ability to mimic the suction effect of a black hole.
The pull is so strong that even light cannot escape it, and anything that gets sucked into her fingertips gets disintegrated. Prime All Might is not immune to these effects, and if he is unable to secure himself, his entire body would be destroyed.
2 Shota Aizawa Should Be Able To Negate One For All
In a one-on-one fight, prime All Might would easily overwhelm Shota Aizawa, who uses a specialized cloth when fighting. Needless to say, All Might would tear that cloth to pieces. Fortunately, Shota's Erasure Quirk would guarantee him victory.
It allows him to erase another person's Quirk, thereby nullifying their power. In order to activate it, Shota must keep his eyes locked on All Might, and he cannot blink otherwise it will deactivate. Erasing One For All would turn All Might back into a frail ordinary human who can be easily subdued.
1 Kai Chisaki Can Manipulate Matter With His Quirk
Kai Chisaki was a Yakuza leader, and he possesses one of the strongest villain Quirks in the series. With Overhaul, he was able to disassemble anything that he touches with his hands, and he can also reassemble things in whatever configuration he wants.
This Quirk basically gives him control over matter, and it can be used to instantly defeat All Might. With a single touch, Kai can literally blow All Might's body apart, and no amount of durability or endurance would be able to stop it from happening.