There are more than a few tough foes in Bleach that pushed the heroes to their limits. One of the three most popular mangas/animes back in the day of it's run (the other two being Naruto and One Piece), gave us a number of truly incredible battles between iconic characters.
Yes, the story has ended and all conflicts have been resolved and all enemies are taken care of, but there were a few characters that initially dominated against our heroes. Whether it is a new threat making a jaw-dropping debut by pummeling the heroes around with ease or the shocking reveal of an enemy's hidden ability, here's the list of Bleach's toughest enemies.
10 Byakuya
Byakuya Kuchiki made a stunning debut as the heartless Soul Reaper. After achieving a few victories against minor hollows, Ichigo faced bitter defeat for the first time when he crossed paths with Byakuya Kuchiki.
Accompanied by his rash lieutenant Abarai Renji, Byakuya was tasked to capture Rukia and send her back to Soul Society. This led to the inevitable confrontation between Ichigo and Byakuya. Although Ichigo stood his own against Lieutenant Renji, Byakuya ended the fight with a single attack, breaking Ichigo's Zanpakuto and leaving a critical wound on his chest.
9 Shunsui
The laid back Soul Reaper of the Gotei Thirteen (Thirteen Court Guard Squads), Shunsui Kyoraku. At first glance, his character came off as comical due to his lackluster attitude and flirtatious personality. It was only after his confrontation with Yasutora Sado that proved that this captain was no joke.
During the invasion of Soul Society by Ichigo and friends, Sado stumbled upon Shunsui. Refusing to let him pass, Sado fires his energy blast at him. The blast zooms toward the seated Shunsui who then easily swipes it away with his bare hands. The Captain then follows up with a counterattack by simply flicking Sado, hurtling him across the field. Shunsui ends the fight with a horizontal slash of his twin blades to Sado's chest, thus marking the heroes' first major defeat on their mission to save Rukia.
8 Grimmjow
Ranked number six of Aizen's Espada division, this ruthless Arrancar's first confrontation with Ichigo in Karakura Town displayed the huge gap between their power levels. The one-sided battle had Grimmjow thrashing Ichigo across town with just his bare fists.
After quite a beating, Ichigo is forced to use his Bankai and release his strongest attack, Getsuga Tensho. He lands the hit but Grimmjow is barely phased by it. Although the fight is interrupted by Tosen, who commands Grimmjow to return to Hueco Mundo, the victor was made clear.
7 Ulquiorra
Thought to be the strongest of the Espada division, it caught Ichigo by a surprise to find out he was only ranked fourth. Ulquiorra was always seen as a powerful enemy, but it was in his clash with Ichigo at Hueco Mundo that he released his final form, enhancing all of his capabilities and dominating against Ichigo.
After a heated battle, Ulquiorra came out as the victor by firing a cero blast through Ichigo's chest and killing him instantly. However, after hearing Orihime's cry, Ichigo revived in a new Hollow form and completely decimated Ulquiorra. Technically this is a loss for Ichigo and a win for Inner Hollow, which isn't great considering the Inner Hollow almost killed Uryu.
6 Harribel
Ranked third in the Espada division, Tier Harribel went toe to toe with Toshiro Hitsugaya in the fake Karakura Town arc. The battle was thought won when Toshiro encapsulated Harribel in his gigantic ice flower prison but with the sudden appearance of Wonderweiss, who let's out a high pitch scream and completely shatters the ice, Harribel is released and unscathed from the Captain's strongest ability.
Once the Visored joined the fight, led by Shinji Hirako, Toshiro was aided by Hiyori Sarugaki and Lisa Yodamaru. Turning it to a three against one fight, but even then Harribel stood her own and couldn't be taken down. It was only after Coyote Starrk's defeat by Shunsui that a disappointed Aizen ruthlessly struck Harribel and ended the fight himself.
5 Barragan
The self-proclaimed God of Hueco Mundo and number two of the Espada. Possessing a dangerous ability to rot anything he touches. In the fake Karakura town arc, he faces Captain Sui Feng and her Lieutenant Marechiyo Omaeda. The fight led to Barragan releasing his final form and Sui Feng losing her left arm by the Espada's deadly touch. Out of options, Sui Feng reveals her Bankai for the first time and fires a huge blast toward the Espada. Struck by the immense explosion, Barragan remained unharmed.
Hachi Ushoda lent his aid to Sui Feng and together they were only able to defeat Barragan by using his own ability against him, thus disintegrating Hueco Mundo's God. Theoretically, this is Barragan losing to himself.
4 Yammy
This one caught everyone off guard. Initially dubbed as the weakest of the Espada, coming in at rank number ten, Yammy ended up being the toughest after releasing his final form in Hueco Mundo. In his gigantic form, the ten imprinted on his skin loses the '1' and reveals he is ranked zero of the Espada.
First revealing his final form to Renji, Sado, and Rukia, he easily disposes of them. Ichigo enters the fray with his new mask equipped and manages to knock Yammy down but not out, despite getting hit by the upgraded Getsuga Tensho.
3 Aizen
The one and only leader of the Espada. There are a couple of times Aizen came out on top, one being the reveal of his betrayal and sinister plan back in Soul Society, but it was in the fake Karakura Town arc where Aizen proved to be the strongest amongst them all.
After the failure of his subordinates, Aizen alone faced the forces of the Gotei 13 and the Visored. A combined effort from both groups did little to no damage. With his Zanpakuto equipped, granting him the power to manipulate his opponent's five senses, he easily defeated his former comrades.
2 Gerrard Valkyrie
Fans that have only watched the anime may not know this character. The anime, unfortunately, stopped before the final arc of the manga, the Thousand Year Blood War. This was a war between the soul reapers of the Gotei 13 and the long thought dead Quincy army, making their vengeful return under the command of Yhwach, son of the Soul king.
Under Yhwach's command, Gerrard Valkyrie proved to be an unkillable Quincy warrior. Facing off against the likes of Toshiro, Byakuya, and Zaraki Kenpachi. Having the ability to increase his body size and strength was bad enough but it's his healing ability that made him such a dangerous opponent. Able to survive the most fatal attacks such as Kenpachi cutting him in two and Byakuya's multiple blades piercing his head. Unable to take down the Valkyrie, Gerrard met his demise by his own leader Yhwach who consumed his Quincy powers and left him as a pile of bones.
1 Yhwach
The final enemy of the series is none other than the Soul King's son. A dangerous foe with the ability to absorb any Quincy power and use it as his own, there's no questioning why he's the leader.
Yhwach first displayed his strength in his invasion of Soul Society where he battled with Captain Commander of the Gotei 13, Genryusai Yamamoto, and brutally ended the fight by slicing the old man in two. Ichigo's first encounter with the Quincy leader also ended in disaster. In an attempt to stop Yhwach from escaping Soul Society, Ichigo was stopped by Quincy general Haschwalth who stepped in and easily broke his Zanpakuto in two. A mere general with that sort of power says a lot about their leader's capabilities.