Aizen Sosuke has one of the scariest zanpakutos in Bleach, which perfectly matches his underhanded, manipulative, and fraudulent character. However, as Gin mentions, it is not the Kyoka Suigetsu’s ability to fear, but the fact that its wearer possesses so much raw reiatsu that it is impossible to defeat it.
However, suppose one looks beyond the perspective of the protagonist of the shonen story. In that case, it can be seen that there are a few Zanpakuto – in their shikai forms – who are capable of defeating Aizen. Similarly, some would have almost no effect on this powerful villain.
10 Could Defeat Aizen: Shinken Hakkyoken – Can absorb and divine beings, so it should work against Aizen.
The ceremonial sword that House Ise maintains, the Shinken Hakkyoken, is pretty useless from a generic combat perspective because it doesn’t even have an edge.
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However, it can absorb the spiritual pressure exerted by so-called « divine beings » and disperse or reflect it. It worked spectacularly against Lille Barro’s final form, so it stands to reason that it would have the same result against Aizen after he undergoes his last Hogyoku transformation.
9 No Chance: Gegetsuburi – He’s extremely weak, so Aizen wouldn’t break a sweat fighting him.
Marechiyo Omaeda’s Gegetsuburi is nothing more than a huge hunk of metal, shaped like a sphere with many pikes protruding from the surface.
It works like a morning star, allowing its user to carry out near and far attacks without leaving the site. Considering that Ichigo managed to destroy it with a single hit, without even entering bankai, it suggests that Aizen would consider the Gegetsuburi a joke.
8 He could defeat Aizen: Nozarashi – Has the power to slice anything he comes in contact with
Kenpachi finally manages to reach the state of communication with his zanpakuto, the Nozarashi, and is as beast as him. Excluding its unnecessarily exaggerated size, this shikai also has the power to smash through just about anything it comes in contact with, even if it is something as intangible as emptiness.
Before manifesting his bankai, Kenpachi’s fight with Gerard Valkyrie shows that Nozarashi is not to be taken lightly. How could Aizen’s hypnosis counteract this shikai’s overflowing animal reiatsu?
7 No Chance: Zangetsu – He’s no match for Aizen, as Ichigo has tried several times.
Zangetsu and Ichigo have tried to take Aizen down multiple times, only succeeding once when Ichigo manifests his full reiryoku and directs it against him in a single black blast of energy.
On his own, this zanpakuto is no match for this villain, even including the fact that Ichigo has not seen the Kyoka Suigetsu’s trigger point and is therefore not affected by her Perfect Hypnosis. Also, all he can do is throw Getsuga Tenshos around him – there’s not much depth or complexity in combat.
6 could defeat Aizen: Ichimonji – Yhwach could be too fast for Aizen to catch up
Ichimonji’s most impressive technique is his ink-based calligraphy: its activation allows its wearer, Ichibei Hyosube, to fragment his opponent (or his abilities) by taking their « names ». It does this by splashing a unique variety of black ink in any direction you choose.
Furthermore, he calls himself a « master » of anything made up of « black », leading to a series of strange but powerful abilities. Most importantly, Ichibei doesn’t take long to launch Yhwach during the first few rounds of their combat, which is proof enough that Ichimonji can destroy Aizen.
5 No Chance: Tenken – The display of power he had during the Karakura Town Arc proved he had no potential
Tenken, Sajin Komamura’s zanpakuto, is a vast projection of his entire body, except that it appears one part at a time. It usually shows the part of the sword, wielded by a discontinuous hand, but it can also produce others.
During the false city of Karakura arc, Komamura draws his bankai – the magnificent Kokujo Tengen Myo’o – to defeat Aizen and avenge his friend. However, it gets through effortlessly, so there is no doubt that your shikai gets the desired result.
4 could defeat Aizen: Minazuki – The wealth of swordsmanship and offensive powers could defeat Aizen
Minazuki is incarnated as a manta ray-type medical creature, though his offensive powers would make the most accomplished Shinigami nervous.
Unohana wields her shikai with recklessness, easily butchering Kenpachi Zaraki and killing him more times than either of them can count. This zanpakuto is reinforced by its inimitable user, the first Kenpachi, whose knowledge of swordsmanship is superior to that of almost all members of Soul Society.
3 No Chance: Sode No Shirayuki – It would be useless in the battle against Aizen as he is too slow
Rukia’s newly developed Sode no Shirayuki is not far behind: it forces her entire physiological temperature to drop drastically, which can carry over into her surroundings.
In her shikai state, she can remove every last ounce of heat from herself, bringing her anatomy to the significant point of Absolute Zero (albeit with a strict time limit not exceeding 4 seconds.) In theory, this technique based on the ice is enough to stop anyone in their path, but battles are rarely about anything other than reiryoku. In short, Aizen is going to vaporize Rukia.
2 He could defeat Aizen: Ryujin Jakka – He’s so powerful that even Aizen planned to avoid him
Ryujin Jakka is so powerful that Aizen actively plans to avoid him: realizing that he would have no chance of conquering the old man with his shikai, he goes to the trouble of creating an entirely new Arrancar, Wonderweiss Margela, with the help of his hogyoku.
This act is carried out to allow the villain access to his ultimate ambition, the Royal Kingdom, as controlling Ryujin Jakka is the only possible way for Aizen to elude the old man. His overly careful strategy is clear proof of the unrivaled intensity of Yamamoto’s shikai.
1 No Chance: Senbonzakura – Byakuya’s Shikai is far superior to its previous editions
Senbonzakura is a spectacular zanpakuto, not to mention how exquisitely beautiful her sakura-themed blooming leaves are. It is very effective in the different facets of combat, from attack to defense, through range and precision.
Following his instructions under the tutelage of the Royal Squad, the Byakuya shikai is far superior to its previous editions, as well as much larger in scope and size. However, all Aizen needs is to free Kyoka Suigetsu once, and no more Senbonzakura.