Not everyone is born naturally gifted and can often struggle to hone their skills for years on end; whereas others always appear to be one step ahead, with their intuitive minds leading the way. Gaining the upper hand over one's enemies doesn't always require brute force, as the most intelligent Bleach characters can attest to.
Some may view Bleach as sensationalized swordplay; however, many characters would argue that there are deeper elements to this revered Big Three shonen series. Each of these experts has practically revolutionized specific fields with their out-of-the-box thinking and innovative contributions (whether morally acceptable or otherwise.)
The following content contains spoilers not yet revealed in the anime's first cours of Bleach: Thousand Year Blood War, currently streaming on Hulu and Disney Plus.
10 Kisuke Urahara (Shinigami)
This great scientific mastermind may not be a Seireitei resident any longer (after being wrongfully exiled for Aizen's crimes), but he has certainly left his mark on the Shinigami's Society and way of life.
Not only is Urahara the originator of the Shinigami Research and Development Institute, but he also founded the groundbreaking Gigai Technology with an assortment of special features, the Shin'eiyaku medication (which will be particularly useful during the Thousand Year Blood War), and much, much more. Additionally, Urahara arguably has the greatest understanding of how Kidō works, creating his own high-level spells, and is also one of only two people in existence to make a Hōgyoku.
9 Jugram Haschwalth (Quincy)
One does not simply become Yhwach's right-hand man and advisor without enough intelligence to back him up, and this blonde beauty has brains by the bucketload. Jugram Haschwalth is often the voice of calm reason when Yhwach allows his emotions to run rampant and is the de-facto leader of the Quincy when the tyrant is otherwise engaged.
This Sternritter Grandmaster has not always had the best self-confidence in his own talents, and so he learned from a very young age to partner up with powerful people for self-preservation (the irony is that he made them stronger by proximity.) Jurgam has been strategizing since day one, and his constant attentiveness has surely assisted in keeping The Balance under control, producing the most favorable outcomes for Yhwach's "other half."
8 Sosuke Aizen (Arrancar Army)
Aizen is essentially the yin to Urahara's yang; the perfect example of what happens when a big thinker gets seduced by the dark side. This highly manipulative psychopath manages to hide his malicious intentions from the Gotei 13 for over a century, barely raising any suspicion during his numerous blood-soaked experimentations.
This Shinigami traitor not only creates the first Hōgyoku but discovers how to control it, and becomes the first to cultivate the distasteful Hollowfication rituals, subsequently creating his Arrancar Army and making himself practically immortal. Aizen also produced the niftyCaja Negación, a pocket-sized, inescapable alternate-dimension prison, and is still ingeniously meddling with the war on Seireitei in the Thousand Year Blood War.
7 Kirio Hikifune (Royal Guard)
This feisty Squad Zero mama arguably offers the most comfort to her visitors, with her ample supply of scrumptious food and compassionate demeanor. Thanks to Kirio's ingenious thinking, she has determined a way to infuse her own Reiatsu into her food, giving it incredible rejuvenating properties in the process.
Kirio does not get much recognition for her greatest accomplishment, which involved the creation of Soul Candy, aka Gikongan, which grants Shinigami the powers to work in the Human Realm by separating one's spirit from their body and using Artificial Souls to fill in the gaps. Urahara eloquently picked up where Kirio left off, and together, the whole Gigai process was completed.
6 Szayelaporro Grantz (Espada)
Aizen's mad scientist is in a league of his own, arguably with only Mayuri posing much of a challenge when it comes to inquisitive sadism. The 8th Espada planned ahead by transforming his own Fracción into emergency energy supplies, perfect for consumption (to boost his own reserves, naturally.)
Szayelaporro also constructs an inescapable labyrinth in Heuco Mundo, with interchanging hallways, which he uses to herd his unfortunate prey to their doom. His scientific mind has an insatiable thirst for knowledge that is ceaselessly assessing individuals' strengths and weaknesses. Szayelaporro contributes greatly to the cause with his multiple Reiatsu controlling Devices and Rokureichū, which could accurately evaluate an enemy's power level.
5 Tōshirō Hitsugaya (Shinigami)
When the word "child prodigy" pops up, the first person to come to mind is the talented Tōshirō, the youngest recorded Gotei 13 Captain in Bleach history. This powerhouse has had an intense connection with Hyōrinmaru since very early on; even before his Shinigami days began, and he surpassed his elders at Shin'ō Academy to graduate early.
Wise beyond his years, "Whitey's" critical thinking has often saved him on the battlefield, not to mention he was one of the few to suspect Gin Ichimaru and eventually connect the dots back to Aizen, uncovering most of his ploy in the process. Hitsugaya has natural talents in combat and detective work; now, he just needs to work on the charm!
4 Askin Nakk Le Vaar (Quincy)
Like any wise warrior, Askin is selective about which battles he participates in and would rather observe and gather information instead of impulsively leaping into action. Not only is he an accomplished Sternritter but Askin is one of four Schutzstaffel, due to his godlike influence and seamless strategizing during combat.
His Deathdealing powers take a great deal of concentration to wield, as Askin has to be constantly thinking about what to ingest and at what level (while taking body mass, genetics, and other pharmacology factors into consideration) so as to create the desired effect. Moreover, Askin analyses his opponent's Reiatsu so swiftly that his counter-move is practically instinctive, virtually concurrent, and unavoidable in most cases.
3 Ichimaru Gin (Arrancar Army)
Gin's genius has been evident since childhood, as he excelled leaps and bounds ahead of his peers, completing the grueling Shin'ō Academy course at break-neck speed and knocking Kaien Shiba off his thrown as the youngest Shinigami initiate.
This snake is the ultimate master of deception and has been pulling the wool over everyone's eyes, even longer than Aizen. Deciding to play the long game, Gin ensures his placement at the traitor's side, earning his trust, and eventually figuring out a way to break Kyōka Suigetsu's seemingly invincible hold. His manipulative mind has proven to be a game-changer on the battlefield, as he seems to always be one step ahead of his opponent.
2 Oetsu Nimaiya (Royal Guard)
The "God of the Sword" may seem flashy, eccentric, and a bit of a party animal, but he forms the very backbone of what it means to be a Shinigami today.
Oetsu is essentially the architect behind Zanpakuto, after somehow finding a way to convert the Reishi from fallen Shinigami back into an energy source while maintaining their individual characteristics. These Asauchi can then be fused into weapons and take up a life of their own; if that's not super-genius intelligence, nothing is! Furthermore, Oetsu can technically wield up to six Bankai simultaneously (which includes his alluring Zanpakuto Spirit assistants.)
1 Mayuri Kurotsuchi (Shinigami)
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Mayuri is arguably the most misogynistic Shinigami in power (besides maybe Iba), however, his brilliant mind and quick-witted comebacks make him more bearable overall. It's probably easier to list the things Mayuri didn't invent, as he always seems to have some new contraption or serum up his sleeve, to perfectly counter each situation.
From his poisons (and cures) to those strange, detatachable body parts, to his Nikubakudan kamikaze bombs, the creation of Fake Karakura Town, and more, the 12th Division Captain is more than well prepared! Mayuri even manages to create a daughter for himself; not in the conventional way, but through successful Gigai experimentations. He is also one of the few known to possess enough skills to repair a Zanpakuto and has turned himself into a virtually indestructible force; an Inspector Gadget Soul Reaper with a rather ruthless side.