History LogicalWeakness / MyHeroAcademia

* To start off, the very nature of his Quirk's [[PowerParasite overall]] [[ComboPlatterPowers function]] and accumulation over generations means he actually has ''more'' logical weaknesses than any Quirk-holder in the series and regularly gets taken off-guard by opponents finding ways to circumvent his powers. In contrast to Izuku learning how to [[RequiredSecondaryPowers balance or cancel out disadvantages]] through careful handling the sheer amount of Quirks All For One has means he realistically can't keep track of the downsides in using them.

* The energy from Rewind renders him [[InvincibleVillain physically immortal]] because it undoes injuries inflicted on him like they never happened. However, since this is '[[FountainOfYouth rewinding]]', not actual healing it means any mutation-type Quirks like Hawks' [[PowerGivesYouWings Fierce Wings]] are reduced to an infantile state on his body and thus effectively useless in fights, limiting his available options in this condition.

* His ability to steal Quirks only works on proper Quirk Factors. In the past, All For One discovered that he couldn't detect Yoichi's Quirk Bestowal because, due to the circumstances of the latter's birth, it was extremely weak and incomplete - meaning that All For One's ability didn't even detect it, and therefore couldn't target it. Likewise, he can't steal One For All's "embers" because they are just weak leftovers of the true Quirk, meaning that there's no proper Quirk Factor to steal.

* According to an InUniverse ConspiracyTheory regarding TheSingularity, Quirks [[AbilityMixing combine to form new and increasingly complex powers]] over generations which become [[PowerIncontinence too difficult to control]]. In addition they're also said to [[PersonalityPowers have an influence on the psyche of their wielders]].

* Users can be ''resistant'' to the effects of their own Quirks but not ''immune''.

* Hawks has feathers that he can control telekinetically. It's a very versatile Quirk that he uses to great effect, essentially giving him flight, telekinesis and a dangerous weapon all in one -- but he's still limited by the fact that he only has so many feathers which means he can only do so many things with them at once. The feathers are also vulnerable to being destroyed in battle, after which he'll need time to regrow them.

* Even with [[SuperpowerfulGenetics hereditary components]] most Quirks don't grant SuperToughness and while users can be born with or somehow gain the RequiredSecondaryPowers they still have limits.

* His power is seriously good but [[HowDoIShotWeb doesn't come with instruction manuals for the Quirks he steals]]. If he wants to be able to use individual Quirks to the levels of their original holders he'll have to train with said Quirks like the real users did and since he has ''so many'' Quirks he's average at best with using individual ones. This is why he prefers BoringButPractical and SimpleYetAwesome powers like SuperStrength and SuperToughness over DifficultButAwesome or AwesomeButImpractical powers like Best Jeanist's [[ClothingCombat control over fibers]] since he can't or [[BrilliantButLazy won't]] put in the effort. Most of the time he depends on [[CombatPragmatist sneak attacks or fighting dirty]].

* He can't [[DiscardAndDraw destroy Quirks once he's taken them]], just keep them and pass them on. This bites him ''hard'' when he takes Star and Stripe's [[RealityWarper New Order]] after killing her; before dying she placed a rule that made it rebel alongside the Quirks he already possessed. He has no way to get rid of them without someone to pass it on to so it just proceeds to whoop his ass from the inside out.

* Shota Aizawa/Eraser Head can [[PowerNullifier nullify]] the Quirks of others by [[NoEyeInMagic staring at them but must maintain his line of sight and cannot blink while doing so]]. This has resulted in eye strain and dryness from prolonged use. He also can't nullify mutation-type Quirks since they're part of the user's body and are always on. After [[EyeScream losing an eye]] during a pivotal battle the utility of his Quirk becomes severely diminished, almost to the point of uselessness.

* Neito Monoma/Phantom Thief can copy the Quirks of those he touches but can only use one Quirk at its base state. One for All is a "dud" to him because he can only copy its power stockpile aspect and doesn't have the time to build up a stockpile. This applies to any Quirk that requires accumulating power -- since he has no time for accumulation to occur he can't use it. He's also limited by his own knowledge and abilities. Quirks with physical requirements may be unsafe or unusable for him and of course he'll lack experience with Quirks he copies unless he's used them before or witnessed them in action.
** Monoma later turns this into a Logical ''Advantage'': if he copies a Quirk that was weakened or crippled he instead gets a base-state version of that Quirk lacking the original's deficiencies. He ends up copying Aizawa's [[AntiMagic Erasure]]. At the time Aizawa had [[EyeScream lost an eye]], therefore losing the ability to use his Quirk; Monoma has no such weakness.

* Even with a [[HealingFactor Super Regeneration]] Quirk he requires constant life support and is dependent on assistance from others for survival. And it's strong but still has limits: If opponents can do enough damage in a short enough period it starts failing. [[AntiRegeneration Certain types of damage can destroy cells so thoroughly]] it can't be undone without a rest period or at all. It'll also automatically work on healing ''any'' damages inflicted without distinction to prioritizing which injury is more important. Thus if he loses an arm and is attacked before it's fully restored, even if it's as minor as an electricity stream only strong enough to stun him Super Regeneration will slow or even stop healing the limb in order to focus on healing the less serious damage and leave him handicapped for a longer period of time.

* Shinso's Quirk allows those under his control to communicate with All For One without any intent at all, following their master's commands. The LivingLieDetector Quirk he has works by sensing malicious intent but fails on Aoyama and his parents when they're luring him into a trap.
* Kurogiri's Warp Gate is an artificial Quirk created by [[AbilityMixing merging Quirks]], meaning it's more powerful than natural Quirks by its nature, including All For One's own warping Quirk. Once the heroes have scattered his forces far enough from one another using Warp Gate there's nothing he can do about it.
* He takes a few seconds to steal Quirks. This means it can be interrupted or allow a counterattack. Star and Stripe could've had her Quirk not be stolen if she'd chosen to, she just had something else in mind.

* All For One is incapable of meaningfully growing as a person due to being TheSociopath and a {{narcissist}} (and is implied to have been ''born this way''). This creates a [[FatalFlaw blindspot]] in his planning as the idea people might not react as he assumed because they've changed is one he's [[EvilCannotComprehendGood fundamentally incapable of understanding]]. This is also implied to hinder his ability to use Quirks he steals as his lack of strong emotions naturally means he's unable to [[EmotionalPowers pour his feelings into Quirks to further empower them]] and thus only uses them at their base strength. It isn't until [[RageBreakingPoint he's so infuriated at the Heroes]] in the final battle that he's able to charge a [[LightEmUp laser beam Quirk]] by fueling it with his anger and knock out [[TheJuggernaut Gigantomachia]] and [[LivingShadow Dark Shadow]].
** And when All For One manages to use his rage to empower his Quirks he goes way overboard due to not being used to strong emotions. As a result he ends up pushing his Quirks far beyond what his body can handle which makes them immensely more powerful at the cost of [[CastFromHitPoints massively damaging his own body]]. In turn [[FountainOfYouth Rewind]] automatically heals his injuries at the cost of [[CastFromLifespan rewinding his age much faster]].
* The rewind energy renders him [[InvincibleVillain physically immortal]] because it rewinds any injuries inflicted on him like they never happened. However, since this is '[[FountainOfYouth rewinding]]', not actual healing it means any heteromorph-type Quirks like Hawks' [[PowerGivesYouWings Fierce Wings]] are reduced to an infantile state on his body and thus effectively useless in fights, limiting his available options in this condition.
* His PowerParasite nature makes it a StoryBreakerPower when facing opponents with Quirks as he can just steal their Quirk and it's virtually over given how most Heroes are dependent on their Quirks. Logically a BadassNormal won't have any Quirk to steal and are used to fighting more powerful enemies, meaning he will have to actually fight them. Normally not an issue given the sheer power disparity but if CharlesAtlasSuperpower is in play or the opponent is using technological enhancements...
* His healing abilities still need time to heal wounds. As such DamageOverTime effectively counters it, or in the case of Rewind continually drains his remaining time at a rapid rate.

* He has to consciously activate individual Quirks as having ''that'' many active all at the same time would be extremely impractical. It's for this reason he very rarely uses mass Quirk combinations like the one he tried against All Might during their first battle in years, normally sticking to a few at a time. He still needs to ''think'' about which Quirks he wants to activate and to what effect; as such blitzing him can prevent him from doing more than frantically [[SpamAttacks spamming Quirks]].
* His Quirk has one in that while it can take any Quirks and seems to have no limit to how many it can take the user does have physical limits the Quirk does nothing to mitigate - and it won't be long before he reaches the limit of his physical strength.
* He's shown repeatedly that while he's capable of stealing any Quirk he can get his hands on except One For All, for his Quirk to activate he needs to physically touch the 'true body' of the holder so those able to avoid being grabbed or attack at a range can avoid losing their Quirks. He likewise cannot steal Quirks by touching anything they produce such as Twice's [[MesACrowd Quirk]] from the cloned variants or Endeavour's Quirk from flaming constructs. Tokoyami {{lampshades}} this as the reason he was selected to provide support with fighting him as [[FightingSpirit Dark Shadow]] is likewise capable of touching him without fear, allowing him to receive physical blows from somebody other than a holder of [[TheImmune One For All]].

* He can't [[DiscardAndDraw destroy Quirks once he's taken them]], just keep them and pass them on. This bites him ''hard'' when he takes Star and Stripe's [[RealityWarper New Order]] after killing her; before dying she placed a rule that made it rebel alongside the other Quirks inside him. He has no way to get rid of it without someone to pass it on to so it just proceeds to whoop his ass from the inside out.
* Shinso's Quirk allows someone under his control to communicate with All For One without any intent at all, following their master's commands. The LivingLieDetector Quirk he has works by sensing malicious intent but fails on Aoyama and his parents when they're luring him into a trap.
* Kurogiri's Warp Gate is an artificial Quirk made by merging Quirks together, meaning it's more powerful than natural Quirks by its nature, including All For One's own warping Quirk. Once the heroes have scattered his forces far enough from one another using Warp Gate there's nothing All For One can do about it.
* He takes a few seconds to steal any Quirk. This means it can be interrupted or allow a counterattack. Star could've had New Order not be stolen if she'd chosen to, she just had something else in mind.
* All For One's Impact Recoil is useless against attacks that don't utilize physical force such as [[PlayingWithFire Endeavor's flames]].
* All For One subjugates the vestiges of those whose quirks he's through force of will, in contrast to how One For All's vestiges advise, guide and mentor Izuku in cooperation with his own willpower. Even somebody as overwhelmingly powerful as All For One can be given pause if they attack him in a group effort.
* He lost all sensory organs above his upper jaw during his battle with All Might and has to rely on stolen sensory Quirks to compensate, which doesn't go so well when his access to his quirks is temporarily disrupted by all of them rebelling against him in unison. After Rewind undoes his disfigurement, he stops using said Quirks, but in exchange, his natural senses can now be disrupted by Quirks that target them, enabling him to fall for an Illusionary target that [[MasterOfIllusion Camie]] created.
* All For One is incapable of meaningfully growing as a person due to being TheSociopath and a {{Narcissist}} (and is implied to have been ''born'' that way). This creates a blindspot in his planning, as the idea people might not react as he assumed because they've changed for the better as people is one he's fundamentally incapable of understanding. This is also implied to hinder his ability to use the Quirks he steals, as his lack of strong emotions naturally means he's unable [[EmotionalPowers to pour his feelings into his Quirks to further empower them]] and thus only uses them at their base strength. It isn't until [[RageBreakingPoint he's so infuriated at the Heroes]] in the final battle, that he's able to charge a [[LightEmUp laser beam Quirk]] by fueling it with his rage, and is able to knock out Gigantomachia and Dark Shadow.
** And when All For One manages to use his rage to empower his Quirks, he goes way overboard with it due to not being used to having strong emotions. As a result, he ends up pushing his Quirks far beyond what his body can handle, which makes them immensely more powerful at the cost of [[CastFromHitPoints massively damaging his own body]]. In turn, [[FountainOfYouth Rewind]] automatically heals his injuries at the cost of [[CastFromLifespan rewinding his age much faster]].
* The rewind energy renders him [[InvincibleVillain physically immortal]] because it rewinds any injuries inflicted on him like they never happened. However, since this is '[[FountainOfYouth rewinding]]', not actual healing, it means that any heteromorph-type Quirks, like Hawks' Fierce Wings, are reduced to an infantile state on his body, and thus effectively useless in a fight, limiting his available options in this condition.
* His PowerParasite nature makes it a StoryBreakerPower when facing opponents with Quirks, as he can just steal their Quirk and it's virtually over given how most Heroes are dependent on their Quirks. Logically, a BadassNormal won't have any Quirk to steal and are used to fighting more powerful enemies, meaning he will have to actually fight them. Normally not an issue given the sheer power disparity, but if CharlesAtlasSuperpower is in play, or the opponent is wearing technological enhancements...
* All his healing abilities still need time to heal wounds. As such, damage over time attacks such as a constant electric shock or acid effectively counter it, or in the case of Rewind, continually drain his remaining time at a rapid rate.

* Kai Chisaki/Overhaul can disassemble and reassemble anything he touches, thus making him extremely dangerous for close-range battles as well as limited long-range since he can reassemble objects long enough to hit opponents with. He can also heal himself and others with his touch, making him an excellent SupportPartyMember as well. But in a similar vein to the "close-range" weakness listed if his opponent zig-zags too much he can't use his Quirk on them. Mirio's Quirk is also this to him and if his arms are taken out in a way he can't react before touching anyone else, like in a surprise attack or while he's restrained which the League takes full advantage of in revenge for the murder of one of their own he's completely useless.

* This is exploited in the Final Exam arc which pits a pair of students against the teacher they'd have the most trouble with (the teachers are going easy on them; the purpose of the test was to see them face their weaknesses, not get [[CurbStompBattle curb-stomped]]).
** Kirishima and Sato, who have time limits on their powers fight against StoneWall Cementoss who can easily beat them in a battle of attrition.
** Yaoyorozu and Todoroki, the students [[SquishyWizard most dependent on their powerful Quirks]] are up against mobile PowerNullifier Aizawa.
** Kaminari and Ashido [[DumbMuscle aren't the brightest]] so they face [[SuperIntelligence Principal Nezu]].
** [[PrehensileTail Ojiro]] and [[SuperSpeed Iida]] face Power Loader who destabilizes the ground so they can't get any leverage to use their abilities.
** Sero and Mineta, whose Quirks are mostly used for sticking others in place are pitted against Midnight, whose Quirk can put them to sleep without her needing to move an inch.
** Squishy-but-mobile Tokoyami and Tsuyu are pitted against [[MesACrowd Ectoplasm]], who can use his power to corner them.
** Jiro and Koda's Quirks both rely on sound so they go against [[SuperScream Present Mic]] and so forth.
** Deku's One for All is still in a development phase while Bakugo is a close-combat master in a heated environment. All Might can overpower them simply by being fast enough for both.

* Flect Turn can [[AttackReflector redirect impacts to their source]] and even briefly store them for later. Though if he tries taking in the energy from repeated blows he'll start moving when hit, release less power and eventually be overcome.

As powerful as Shigaraki/All For One is, like any person and/or Quirk he has weaknesses stemming from both his personal nature and that of his Quirk. Unfortunately for him the heroes figure them out and exploit them repeatedly, especially during the FinalBattle.
* To start off the very nature of his Quirk's [[PowerParasite overall]] [[ComboPlatterPowers function]] and accumulated powers over the generations means he actually has ''more'' logical weaknesses than any single Quirk-holder in the series and regularly gets taken off-guard by opponents finding ways to circumvent his powers. In contrast to Izuku learning how to [[RequiredSecondaryPowers balance or cancel out the disadvantages]] of his less multiple powers through careful handling the sheer amount of Quirks All For One has means he realistically can't keep track of the downsides in using them.
* All For One's power is seriously good but [[HowDoIShotWeb doesn't come with instruction manuals for the Quirks he steals]]. If he wants to be able to use individual Quirks to the levels of their original holders he'll have to train with said Quirks like the real users did and since he has so ''many'' Quirks he's average at best with using any individual ones. This is why he prefers BoringButPractical and SimpleYetAwesome powers like SuperStrength and SuperToughness over DifficultButAwesome powers like Best Jeanist's [[ClothingCombat control over fibers]] since he can't afford to put in the time to train it to full level. Most of the time he depends on [[CombatPragmatist sneak attacks or fighting dirty]].
* All For One has to consciously activate individual Quirks as having ''that'' many active all at the same time would be extremely impractical. It's for this reason he very rarely uses mass Quirk combinations like the one he tried against All Might during their first battle in years, normally sticking to a few at a time. He still needs to ''think'' about which Quirks he wants to activate and to what effect; as such blitzing him can prevent him from doing more than frantically [[SpamAttacks spamming Quirks]].

* He's shown repeatedly that while he's capable of stealing any Quirk he can get his hands on except One For All, for his Quirk to activate he needs to physically touch the 'true body' of the holder so anyone fast and agile enough to avoid being grabbed or able to attack at a range can avoid losing their Quirks. He likewise cannot steal Quirks by touching anything they produce such as Twice's [[MesACrowd Quirk]] from the cloned variants or Endeavour's Quirk from flaming constructs. Tokoyami {{lampshades}} this weakness as the reason he was selected to provide support with fighting him as [[FightingSpirit Dark Shadow]] is likewise capable of touching him without fear, allowing him to receive physical blows from somebody other than a holder of [[TheImmune One For All]].
* Even with a [[HealingFactor Super Regeneration]] Quirk he requires constant life support and is dependent on assistance from others for survival.
* His Super Regeneration is strong but has limits like any other. If an opponent can do enough damage in a short enough period it starts failing. [[AntiRegeneration Certain types of damage can destroy cells so thoroughly]] it can't undo the damage without a rest period. It also will automatically work on healing ''any'' sort of damage inflicted without distinction to prioritizing which kind of injury is more important than others. Thus if All For One loses an arm and is attacked before it's fully restored, even if it's as minor as a stream of electricity only strong enough to stun him; Super Regeneration will slow or even stop healing the limb in order to focus on healing the less serious damage and leave him handicapped for a longer period of time.
* All For One's Quirk means he can't [[DiscardAndDraw destroy Quirks once he's taken them]], just keep them and then pass them on. This bites him in the ass ''hard'' when he takes Star and Stripe's [[RealityWarper New Order]] after killing her; before dying she placed a rule that made it rebel and attack the other Quirks inside him when. He has no way to get rid of it without someone to pass it on to so it just proceeds to whoop his ass from the inside out.
* Shinso's quirk allows someone under his control to communicate with All For One without any intent at all, following their master's commands. The Living Lie-Detector Quirk he has works by sensing malicious intent but fails on Aoyama and his parents when they are luring him into their trap.
* Warp Gate is an artificial Quirk made by merging multiple Quirks together, meaning it's more powerful than a natural Quirk by its nature, including All For One's own warping Quirk. Once the heroes have scattered his forces far enough from one another using Warp Gate, there's nothing All For One can do about it.
* All For One takes a few seconds to steal any Quirk. This means it can be interrupted or allow a counterattack. Star could have ordered New Order not to be stolen if she'd chosen to, she just had something else in mind.
* All For One's Impact Recoil is useless against attacks that don't utilize physical force, such as [[PlayingWithFire Endeavor's flames.]]

* Izuku Midoriya/Deku can use One For All to amplify his physical strength, speed and durability as a form of MagicEnhancement but it still puts enormous strain on his body. At first he literally can't use it without severely injuring himself and even after practice and training he can only use a tiny portion of its total power safely. Most of Midoriya's troubles with One for All seem to stem from the fact he was given the power rather than being born with it so he lacks both the physical conditioning and years of experience most people gain from having Quirks at a young age.

* Cathleen Bate/Star and Stripe's Quirk allows her to [[RealityWarper assign "rules" to a target she has touched and called out their name, limited to two at a time]]. But in order to use this she needs to touch a target and call its name. Thus if she does not know the name or the person is experiencing identity issues such as Shigaraki's struggle with the merged consciousness of All For One then her power is ineffective. Furthermore, because of how powerful her Quirk is she can only create two rules at once. In most cases she can use the first rule on herself, leaving her able to switch the second rule on the fly. If she has to use more than two rules she needs to cancel one in order to create a new one. In addition, Star's Quirk is hampered by her personality much like Sir Nighteye's was: While almost always using one rule to give herself SuperStrength she has a hard limit to how much stronger she can make herself as All Might left such a lasting impression that she can't imagine surpassing him.

* Nemuri Kayama/Midnight has the ability to [[KnockoutGas put anybody to sleep with her Quirk which shows up as a violet mist]]. However, someone holding their breath will prevent this from working. While someone can't hold their breath forever they can at least do so long enough to get away if they know she's coming. Also, it takes time to take effect so it's not an instant knockout. Finally, [[CloseRangeCombatant Midnight can only eminate this gas from her body]] which means she has to get up close and personal for it to work. This can be exploited with long-range Quirks simply staying out of Midnight's range or Mineta's sticky orbs keeping Midnight locked in place and unable to reach him with her Quirk. This is also what leads to her death as a sneak attack from Mr. Compress leaves her heavily injured with a group of villains running to attack. She simply can't create enough gas to cover them in time and is KilledOffscreen.
* Eri has a unique Quirk: "Rewind", which lets her literally turn back the clock on the body of anyone she touches. While this may sound like an awesome HealingHands Quirk it has the potential to kill as a body she rewinds can have old wounds reopen and life-saving medical procedures undone. When her power first manifested she accidentally rewound her father to the point that he ''[[CessationOfExistence ceased to exist]]''; the combination of her inexperience with this Quirk and the resultant trauma compounded by the abuse she suffered while held captive by Overhaul only made it harder for her. It isn't until she's freed from his grasp and taken into a loving, caring environment that she's able to start learning to control it. This is what allows her to restore Mirio's Quirk after it had been lost to one of Overhaul's anti-Quirk bullets by rewinding his body back to before he was struck with the bullet.

As powerful as Shigaraki/All For One is, like any person and/or Quirk he has weaknesses stemming from both his nature and that of his Quirk. Unfortunately for him the heroes figure them out and exploit them repeatedly, especially during the FinalBattle.
* To start off the very nature of his Quirk's [[ComboPlatterPowers function]] and accumulated powers over the generations means he actually has ''more'' logical weaknesses than any single Quirk-holder in the series and regularly gets taken off-guard by opponents finding ways to circumvent his powers. In contrast to Izuku learning how to [[RequiredSecondaryPowers balance or cancel out the disadvantages]] of his less multiple powers through careful handling the sheer amount of Quirks All For One has means he realistically can't keep track of the downsides in using them.
* All For One's power is seriously good but [[HowDoIShotWeb doesn't come with instruction manuals for the Quirks he steals]]. If he wants to be able to use individual Quirks to the levels of their original holders he'll have to train with said Quirks like the real users did and since he has so ''many'' Quirks he's average at best with using any individual ones. This is why he prefers BoringButPractical and SimpleYetAwesome powers like SuperStrength and SuperToughness over DifficultButAwesome powers like Best Jeanist's [[ClothingCombat control over fibers]] since he can't afford to put in the time to train it to awesome level. Most of the time he depends on [[CombatPragmatist sneak attacks or fighting dirty]].
* All For One has to consciously activate individual Quirks as having ''that'' many active all at the same time would be extremely impractical. It's for this reason he very rarely uses mass Quirk combinations like the one he tried against All Might, normally sticking to one or two at a time. He still needs time to ''think'' about which Quirks he wants to activate and to what effect, as such blitzing him so quickly he has no time to think can prevent him from doing more than frantically spamming Quirks.
* His Quirk has one in that while it can take any Quirk and seems to have no limit to how many Quirks it can take the user does have physical limits the Quirk does nothing to mitigate - and it won't be long before he reaches the limit of his physical strength.
* He's shown repeatedly that while he is capable of stealing any Quirk he can get his hands on except One For All, for his Quirk to activate he needs to physically touch the 'true body' of the holder so anyone fast and agile enough to avoid being grabbed or able to attack at a range can avoid losing their Quirks. He likewise cannot steal Quirks by touching anything they produce such as Twice's [[MesACrowd Quirk]] from the cloned variants or Endeavour's Quirk from flaming constructs. Tokoyami {{Lampshades}} this weakness as the reason he was selected to provide support with fighting him as [[FightingSpirit Dark Shadow]] is likewise capable of touching him without fear, allowing him to receive physical blows from somebody other than a holder of [[TheImmune One For All]].

* Neito Monoma/Phantom Thief can copy the Quirks of those he touches but can only use one Quirk at its base state. One for All is a "dud" to him because he can only copy its power stockpile aspect and doesn't have the time to build up a stockpile. This applies to any Quirk that requires accumulating power -- since he has no time for the accumulation to occur he can't use it. He's also limited by his own knowledge and abilities. Quirks with physical requirements may be unsafe or unusable for him and of course he'll lack experience with Quirks he copies unless he's used them before or witnessed them in action.
** Monoma later inverts this into a Logical ''Advantage'': if he copies a Quirk that was weakened or crippled in some way he instead gets a base-state version of that Quirk lacking the original's weakness. He ends up copying Aizawa's [[AntiMagic Erasure]]. At the time Aizawa had [[EyeScream lost an eye]], therefore losing the ability to use his Quirk; Monoma has no such weakness.

* Mirio Togata/Lemillion possibly has it worst: He can make himself [[{{Intangibility}} intangible]] but has none of the RequiredSecondaryPowers. While intangible he can't see, hear or even breathe as every particle travels through him. He's also still affected by gravity so every act of passing through things becomes a complicated process so he doesn't fall through the ground, though thankfully he ''is'' immune to TeleFrag. By the present he's practiced enough to put the 'awesome' back in DifficultButAwesome but for a while the Quirk was worse than useless. He also phases out of most clothing while using his power, leaving him naked: His hero suit was created using fibers from his hair so he wouldn't accidentally phase out of them while on the job.

** His brother Toya Todoroki wasn't so lucky as he got an extreme version of his father's powers... but inherited the weakness to fire from his mother. He's better known as Dabi of the [[LegionOfDoom League of Villains]]. You know, the guy who basically has ''his burnt skin stapled to his body''?

* Neito Monoma/Phantom Thief can copy the Quirks of those he touches but can only use one Quirk at its base state. One for All is a "dud" to him because he can only copy its power stockpile aspect and doesn't have the time to build up a stockpile. This applies to any Quirk that requires accumulating power -- since he has no time for the accumulation to occur he can't use it. He's also limited by his own knowledge and abilities. Quirks with physical requirements may be unsafe or unusable for him and of course he'll lack experience with Quirks he copies unless he's used them before.

* Mirio Togata/Lemillion possibly has it worst: He can make himself intangible but has none of the RequiredSecondaryPowers. While intangible he can't see, hear or even breathe as every particle travels through him. He's also still affected by gravity so every act of passing through things becomes a complicated process so he doesn't fall through the ground, though thankfully he ''is'' immune to TeleFrag. By the present he's practiced enough to put the 'awesome' back in DifficultButAwesome but for a while the Quirk was worse than useless. He also phases out of most clothing while using his power, leaving him naked: His hero suit was created using fibers from his hair so he wouldn't accidentally phase out of them while on the job.
* Kai Chisaki/Overhaul can disassemble or reassemble anything he touches, thus making him extremely dangerous for close-range battles as well as limited long-range since he can reassemble objects long enough to hit opponents with. He can also heal himself and others with his touch, making him an excellent SupportPartyMember as well. But in a similar vein to the "close-range" weakness listed if his opponent zig-zags too much he can't use his Quirk on them. Mirio's Quirk is also this to him and if his arms are taken out in a way he can't react before touching anyone else, like in a surprise attack or while he's restrained which Shigaraki and Mr. Compress take full advantage of in revenge for Magne's murder he's completely useless.
* Hitoshi Shinso can MindControl anyone who speaks to him, but only if they verbally respond to what he says. Anyone who knows this can safely avoid its effects by remaining silent. His Quirk also won't activate if his voice is electronically altered such as speaking though a megaphone or electronic voice-changer since technically the voice would be the device's and not his. He compensates for this with a special mask that can alter the sound of his voice without a filter though it requires precise adjustments.

* Quirks can also be subjected to a user's [[EmotionalPowers emotions]], [[PsychoactivePowers state of mind]] and physical well-being; in addition they [[HowDoIShotWeb always require training to master]].

* Momo Yaoyorozu/Creati can create objects from her body but needs materials to create them and must understand the specifics of exactly what she's creating (i.e. to create salt she must be aware "salt" consists of [=NaCl=]). She's a BigEater to compensate but is still limited in how much she can make at a time. Since the objects come out of her skin (it's really not as bad as it sounds) she's limited in how large of an object she can make and often has to make bigger things in pieces. She also has to be a TeenGenius just to understand the necessary science to even use her Quirk in the first place.

** After getting additional Quirks through receiving a copy of All For One's Quirk he gains the weaknesses of those Quirks as well: A [[BarrierWarrior shield of solid air]] can only take so much damage, [[BlastingTime lasers]] and [[BlowYouAway wind blasts]] can be dodged, [[SuperSenses detection]] can be avoided, an extra limb that's [[SummonMagic only projected]] can be dispelled and some forms of [[HealingHands cellular regeneration]] don't affect certain blood types. Carrying all those Quirks and using them in rapid succession only makes his physical breakdowns more frequent.

* Shota Aizawa/Eraser Head can [[PowerNullifier nullify]] the Quirks of others by staring at them but must maintain his line of sight and cannot blink while doing so. This has resulted in eye strain and frequent dryness from prolonged use. He also can't nullify mutation-type Quirks since they're part of the user's body and are always on. After [[EyeScream losing an eye]] fighting Tomura Shigaraki and All For One the utility of his Quirk becomes severely diminished, almost to the point of uselessness.
* Shoto Todoroki overheats when using his [[PlayingWithFire fire powers]] and freezes over when using his [[AnIcePerson ice powers]] while the former and latter are also the LogicalWeakness to his father Enji Todoroki/Endeavor and mother Rei Todoroki. He was the product of an ArrangedMarriage for the specific purpose of creating a child with a hybrid ice-and-fire Quirk whose weaknesses would cancel each other out. However, he still ''has'' weaknesses: Since he emits fire from his left side and ice from his right at close range he has difficulty getting the correct one pointed at the enemy. He also has difficulty using them at the same time since they just cancel themselves if he's not careful and switching can give enemies an opening.

** Deku's One for All is still in development phase while Bakugo is a close-combat master in a heated environment. All Might can overpower them simply by being fast enough for both.
* Hawks has feathers that he can control telekinetically. It's a very versatile Quirk that he uses to great effect, essentially giving him flight, telekinesis, and a dangerous weapon all in one -- but he's still limited by the fact that he only has so many feathers, which means he can only do so many things with them at once. The feathers are also vulnerable to being destroyed in battle, after which he'll need time to regrow them.
* The Nomu brought to the training dome has a shock absorption Quirk which lets it survive even a full Detroit Smash from Midoriya. But as All Might notes it's shock ''absorption'' and not shock ''nullification'' which means there's eventually a limit to how many impacts the Nomu can take, a limit All Might's relentless attacks eventually surpass.
* Re-Destro can use the everyday stress he accumulates to increase his strength and size but that only extends to his body which means the prosthetic legs he gets after his fight with Shigaraki remain the exact same no matter how strong he gets and even snap under his weight.
* Lady Nagant subverts this. During their fight Midoriya attempts to capture Nagant by using an entire office building as cover to close the distance, reasoning that a sniper like her would be vulnerable in close quarters. Unfortunately for him she's been trained to deal with close-range fighters, worming her way out of his grip before assailing him with a barrage of bullets from all directions. It's played straight later on, however; for all the power and combat abilities her Quirk has it ultimately boils down to having [[ArmCannon a sniper rifle in her right arm]]. ''Exclusively'' her right arm. Shattering it effectively renders Nagant powerless and unable to use her Quirk despite still being capable of moving on her own.
* Mt. Lady's quirk [[GiantWoman causes her to grow into a giantess]] at 67'8" (2062 cm) tall. And while Mt. Lady's costume has been designed to grow with her this doesn't include shoes so she has to be careful [[AgonyOfTheFeet to not hurt her feet]]. Also, being so big means it's very easy for Mt. Lady to cause property damage so she tries to grow in spaces that can contain her -- when she grew into a giantess in the middle of a crowded city she was shown having to be extremely careful with her movements lest she hurt innocents. Also, GiantEqualsInvincible is not a thing with her; she's certainly stronger and tougher than the average person when giant but can still be hurt by other Quirk-users if they're strong enough. Plus, just like with her feet not being able to have shoes Mt. Lady's costume can't contain any padding or armor to help her cover this weakness since it can't grow with her. All For One even put her on the receiving end of a OneHitKO when she was in giant form, both to show his own power and that she wasn't invulnerable.
* [[GenkiGirl Toru Hagakure]] has {{invisibility}} as her power [[RunningGag which leads to]] [[InvisibleStreaker her having to spend most of her time naked]] in order to be effective since she can't make clothing invisible. She also can't turn it off, even if she's sleeping or unconscious so she has to be careful of things like cars or obstacles in the environment that won't see her. Finally, it's mentioned that [[ExposedToTheElements extreme heat or extreme cold makes her very uncomfortable]]. And since she has to be naked to make the most effective use of her Quirk this can lead to things like coughing or sneezing giving her away. Also, Todoroki once stopped Toru completely by using his ice powers to freeze her to the ground, mentioning that [[AgonyOfTheFeet if she moves the ice would cause her to tear the skin right off of her feet]]. Toru is good for espionage and little else because of her Quirk; even then it comes with several caveats and ways that she could still be detected. Even after her Quirk is expanded to be a light refraction ability instead of just invisibility she's still not much more useful than before. In fact, it's shown that [[PowerIncontinence this power can be overtaxed]] when she uses her refraction to deflect a blast from Aoyama's and becomes completely visible.

As powerful as All For One is, like any person and/or Quirk he has weaknesses stemming from both his nature and that of his Quirk. Unfortunately for All For One the heroes figure them all out and exploit them repeatedly, especially during the FinalBattle.
* To start off the very nature of his Quirk's [[ComboPlatterPowers function]] and accumulated powers over the generations means that he actually has ''more'' logical weaknesses than any single Quirk-holder in the series and regularly gets taken off-guard by opponents finding ways to circumvent his powers. In contrast to Izuku learning how to [[RequiredSecondaryPowers balance or cancel out the disadvantages]] of his less multiple powers through careful handling, the sheer amount of Quirks All For One has means he realistically can't keep track of all the different downsides in using them.
* All For One's power is seriously good but [[HowDoIShotWeb doesn't come with instruction manuals for the Quirks he steals]]. If All For One wants to be able to use individual Quirks to the level of their original users he's going to have to train with said Quirks like the real user did and since he has so ''many'' Quirks he's average at best with using any individual one. This is why he prefers BoringButPractical and SimpleYetAwesome powers like SuperStrength and SuperToughness over DifficultButAwesome powers like Best Jeanist's control over fibers since he can't afford to put in the time to train it to awesome level. Most of the time he depends on sneak attacks or fighting dirty.
* All For One has to consciously activate individual Quirks as having ''that'' many Quirks active all at the same time would be extremely impractical. It's for this reason he very rarely uses mass Quirk combinations like the one he tried against All Might, normally sticking to one or two at a time. He still needs time to ''think'' about which Quirks he wants to activate and to what effect, as such blitzing him so quickly he has no time to think can prevent him from doing more than frantically spamming Quirks.
* His Quirk has one in that, while it can take any Quirk and seems to have no limit to how many Quirks it can take, the user does have physical limits which the Quirk does nothing to mitigate - and it won't be long before he reaches the limit of his physical strength.
* He's shown repeatedly that while he is capable of stealing any Quirk he can get his hands on except One For All, for his Quirk to activate he needs to physically touch the 'true body' of the holder, so anybody who is fast and agile enough to avoid being grabbed by him, or is able to attack at range, will be able to avoid losing their Quirk. He likewise cannot steal a Quirk by touching anything the Quirk produces, such as Twice's [[MesACrowd Quirk]] from any of the cloned variants, or steal Endeavour's Quirk if he's attacked by flaming constructs. Tokoyami {{Lampshades}} this weakness as the reason he was selected to provide support with fighting him, as [[FightingSpirit Dark Shadow]] is likewise capable of touching him without fear, allowing him to receive physical blows from somebody other than a holder of [[TheImmune One For All]].
* Even with a Super Regeneration Quirk he requires constant life support and is dependent on assistance from others for survival.
* His Super Regeneration is extremely strong, but it has limits like any other. If an opponent can do enough damage in a short enough period, it can start failing. [[AntiRegeneration Certain types of damage can destroy cells so thoroughly]] that it can't undo the damage without a rest period. It also will automatically work on healing ''any'' sort of damage inflicted, without any distinction to prioritizing which kind of injury is more important than others. Thus if All For One has lost an arm, and he is attacked before it is fully restored, even if it's as minor as a stream of electricity only strong enough to stun him; Super Regeneration will slow or even stop healing the limb in order to focus on healing the much less serious damage, and leave him handicapped for a longer period of time.
* All For One's Quirk means he can't destroy Quirks once he's taken them, just keep them and then pass them on. This bites him in the ass ''hard'' when he takes Star and Stripe's [[RealityWarper New Order]] after killing her; before dying, Star placed a rule on it that made it rebel against All For One and attack all of the other Quirks inside of him when he takes it. He has no way to get rid of it without someone to pass it on to, so it just proceeds to whoop his ass from the inside.
* Shinso's quirk allows someone under his control to communicate with All For One without any intent at all, following their master's commands. The Living Lie-Detector Quirk he has works by sensing malicious intent, but fails on Aoyama and his parents when they are luring him into their trap.
* Warp Gate is an artificial Quirk made by merging multiple Quirks together, meaning it is more powerful than a natural Quirk by its nature, including All For One's own warping Quirk. Once the heroes have scattered his forces far enough from one another using Warp Gate, there's nothing All For One can do about it.

* Quirks relying on close-range combat and/or touch are limited by a user's ability to get close in the first place. Against clever opponents or those with mobility and range-based Quirks this becomes a problem.

* Most Quirks don't grant SuperToughness and while users can be born with or somehow gain the RequiredSecondaryPowers they still have limits.

* Shota Aizawa/Eraser Head can [[PowerNullifier nullify]] the Quirks of others by staring at them but must maintain his line of sight and cannot blink while doing so. This has resulted in eye strain and frequent dryness from prolonged use. He also can't nullify mutation-type Quirks since they're part of the user's body and are always on. After [[EyeScream losing an eye]] fighting Tomura Shigaraki/All For One the utility of his Quirk becomes severely diminished, almost to the point of uselessness.