There are several useful Transformation Quirks in My Hero Academia, but some of them come with significant drawbacks.

The Quirk in My Hero Academia is similar to the X-gene in X-Men — a biological factor that imbues its user with special abilities, turning them into superpowered entities. The first few Quirk-ed individuals were ostracized and mistreated by society, at least until 80% of the world's population began displaying them.

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These so-called Meta Abilities can be categorized into three basic types: Emitters revolve around manipulating energy and objects, Heteromorphs generate permanent anatomical alterations, and Transformers temporarily modify the user's body. Transformation Quirks are often useful, like Seiji Shishikura's Meatball, Edgeshot's Foldabody, and Kamui Woods' Arbor, while others are relatively counterproductive.

The Chainsaw Nomu is probably one of the weakest Artificial Humans in the story. It accompanies the Vanguard Action Squad to the Forest Training Camp arc, and answers solely to Dabi during the mission. This mold-green creature has six limbs emerging from its muscular torso, each armed with a unique construction apparatus: four chainsaws, a claw hammer, and a drill.

The Tool Arms Quirk is incredibly risky to use, since the slightest misstep could cause irreparable harm to the Chainsaw Nomu's body. More importantly, it's not strong enough to wield multiple Quirks.

Rikiya Yotsubashi, or Re-Destro, leads the Meta Liberation Army until Tomura Shigaraki defeats him and takes over the position. His Stress Quirk is highly potent — it allows Re-Destro to accumulate any feelings of hatred, rage, anxiety, and resentment, subsequently transforming his tension into concussive force.

In other words, the strength of his Quirk is directly proportional to his blood pressure. The problem, however, is that Stress induces an overall negative experience for its user, resulting in Re-Destro's unstable behavior patterns.

Cow Lady, one of the first American Pro Heroes in the story, appears in My Hero Academia: Two Heroes. Her fashion aesthetic incorporates rodeo themes, such as bovine belt buckles, Stetson hats, and cowboy boots. Cow Lady's Cow Quirk is analogous to Froppy's Frog, Hound Dog's Dog, Mirko's Rabbit, and Ryukyu's Dragon.

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Unfortunately, the most she can do is metamorphose into a cow-human hybrid with relatively enhanced stamina and attack power. This doesn't mean that Cow Lady is an incompetent hero, but that her Quirk is sorely limited in terms of scope and application.

All For One possesses a nigh-omnipotent ability. He seizes control of the criminal underworld and establishes himself as the self-titled Demon Lord with nothing more than his All For One Quirk. He has managed to steal extremely valuable Quirks over time, like Warping, Air Cannon, Radiowaves, Life Force, Hardflame Fan, Search, and Impact Recoil.

On the other hand, not every Quirk in All For One's stolen library can be considered beneficial. For instance, he only employs Rivet in conjunction with Multiplier, Air Walk, Springlike Limbs, Spearlike Bones, Hypertrophy, Strength Enhancers, and Kinetic Boosters. It's unclear how practical Rivet actually is.

Dio and Ena, better known as The Serpenters, are a pair of villainous minions in My Hero Academia: World Heroes' Mission. The Serpenters are undeniably powerful, overwhelming most opponents with a combination of fluid movement and brute force. Like the villain Moonfish, these identical twins have a blade-based Quirk named Sword Kill.

This ability converts their lower arms into whip swords, although Trigger, a Quirk-boosting drug, allows them to generate blades from their mouths and backs. The Serpenters are eventually defeated by Katsuki Bakugo, who turns their own Quirk against them.

Hiryu Rin of Class 1-B is an adept fighter, rapidly adapting to his opponent's combat style in the heat of battle. His Quirk produces a sturdy epidermis of snake-like scales, which simultaneously functions as armor as well as artillery. Rin develops several Super Moves, including Sprouting Scales, Reverse Scales, and Within One.

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​​​​​​​The durability of his carapace depends on a calcium-rich diet, but this isn't the main problem with this Quirk. Rin's Scales is significantly weaker than Tetsutetsu's Steel and Kirishima's Hardening, leaving him helpless against stronger attacks.

The Eight Bullets are the first line of defense for the Shie Hassaikai and, by extension, Kai Chisaki. He falls for Overhaul's manipulative charms and dedicates his life to serving the Yakuza's "young master." While he's quite proficient with his Quirk, Hojo's Crystallize is most effective when bolstered by Toya Setsuno's Larceny and Soramitsu Tabe's Food.

Although this Quirk creates a dazzling array of impenetrable crystals, these mineral outgrowths are susceptible to breakage. Further, Hojo's hair gets in the way of Crystallize, a rather annoying disadvantage.

Mirio's Permeation Quirk turns his body intangible to all forms of matter, allowing him to effortlessly navigate through both solids and liquids. He becomes a star UA student after mastering the nuances of his complicated Quirk, making him a hero worthy of inheriting One For All (according to Sir Nighteye).

On the flip side, Mirio's father explains that his innate ability is ill-suited to combat because it is extremely difficult to handle properly. In fact, Permeation can only be used by self-assured people like Mirio, as it would arguably be a death sentence for weaker-willed wielders.

Kiruka Hasaki is a major villain in My Hero Academia: Heroes Rising. She assists Nine on his mission to acquire Katsuma Shimano's Cell Activation ability. Kiruka's Slice Quirk is restricted to her hair, which she transforms into various shapes and structures, from close-range blades and projectile needles to makeshift shields and barriers.

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However, her Quirk remains vulnerable to chemical deterioration, as seen when Mina Ashido's Quirk successfully dissolves her hair. Kiruka is incapacitated by Ashido's Acid Shot, consequently losing the battle.

Those who don't pass the Provisional Hero License Exam are forced to take a Remedial Course program. Gang Orca unleashes a horde of primary schoolers into the UA gym and orders the failed UA students to "communicate with them through [their] hearts."

The small kids promptly reveal their eerily overpowered Quirks, such as Assault Dust, Binging Balls, Viral Cosmos, King Slam, Hula Hoop, Electromagnetic Bullet, and Queen Beam. The most formidable of them all is Tongue Tank, which spawns a mini-cannon from its wielder's mouth. This Quirk is dangerous even when used by accomplished combatants, let alone five-year-old children.

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