The world of My Hero Academia is populated with hundreds of unique quirks, meaning it's only natural for a few to bear some similitude. However, two quirks in particular are uncannily similar, with just minor differences in their mechanics. These quirks are Kirishima’s “Hardening” and Tetsutetsu’s “Steel,” two powers that work on essentially the same principle, yet their mechanics differ greatly.

With such striking similarities between the two, it’s only natural for My Hero Academia fans to wonder which quirk would come out on top if Kirishima and Tetsutetsu were to duke it out. Since Hardening and Steel bear the basic principle of altering the skin’s density and thickness to extreme levels, the answer to this raging question lies in the weaknesses and downsides of the two powers.

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Two Impenetrable Defenses

In principle, both Tetsutetsu and Kirishima possess the same power of hardening their bodies, but the method used to attain this feat is quite different. Kirishima’s Hardening works by making any part of his body rock solid, enough to bear the weight of tons of falling debris. Using the same hardness, he can break through barriers with force, without sustaining any injuries.

Tetsutetsu has similar attributes, but his quirk turns his entire body into steel. In some ways, Steel is more durable than its Hardening counterpart due to steel’s hardness already being set at a certain limit. Hardening, on the other hand, isn’t tied to a fixed durability, a trait that could serve as both a benefit and a drawback. This means that, theoretically, Hardening could become even stronger than Steel, but it would require tremendous time and training.

Hardening and Steel Have Different Adaptability

The major difference between Hardening and Steel lies in their adaptability to external attacks. Since Steel grants Tetsutetsu the exact properties of steel, he can’t strengthen his quirk further than the material’s preset durability. Moreover, the strength and duration of his Steel is dependent on the amount of iron in his diet, meaning he has to replenish his body’s iron reserves by eating foods rich in the element or by directly eating metal.

Hardening isn’t dependent on any sort of external element, meaning the durability of this quirk relies entirely on Kirishima’s own willpower. However, he can increase the potency of his Hardening quirk through specialized training that involves constantly attacking him in his hardened state. Overtime, the quirk becomes stronger and harder, granting Kirishima much more strength and resistance. This puts Hardening at an advantage, as the quirk requires no external elements and its resistance can be increased beyond Steel’s capabilities.

Drawbacks of Hardening and Steel

Akin to every other quirk in My Hero Academia, Hardening and Steel are weighed down by a few weaknesses and limitations. Since the two possess seemingly equal strength, it all boils down to the limitations weighing each quirk down. The two quirks share rather similar weaknesses, with both quirks dissipating after a certain duration. However, the difference lies in how the two quirks are eventually exhausted.

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Using Steel for too long puts Tetsutetsu in a state of iron fatigue, weakening Steel’s impenetrability and durability. On the other hand, Hardening isn’t weakened by using the quirk for too long. Instead, the quirk has a limit to how much damage it can withstand, after which it begins to fade. However, Kirishima was eventually able to refortify Hardening through sheer willpower, negating this limitation all together. This further puts Hardening above Steel, as the latter is dependent on external iron for refortification.

Final Verdict — Hardening Triumphs Steel

With both quirks being almost exact replicas of each other, it's certainly an ardent task to deem one stronger than the other. While the two quirks are neck-and-neck in terms of every aspect, ranging from durability to strength, there are two elements where Hardening triumphs over Steel. These aspects define Hardening as superior to Steel, finally settling the debate about their uncannily similar strengths.

First, Tetsutetsu’s Steel is limited to the properties of its element, meaning the extent of his power is confined to the hardness and durability of Steel. However, Kirishima’s hardening poses no such limitation, meaning he could theoretically achieve the same hardness as a diamond. To put this into perspective, steel is ten times weaker than diamond, and several other elements out there are much harder than steel.

Secondly, Steel is heavily reliant on external sources of iron, and Tetsutetsu is forced to either stay on an iron-rich diet or keep iron on-hand to satiate the quirk’s needs. Hardening has no such external requirement, allowing Kirishima to refortify his quirk without relying on any other elements. With higher strength and durability, coupled with complete self-sufficiency, Kirishima’s Hardening clearly comes out on top as the superior quirk.

My Hero Academia is available to stream on Prime Video.

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