In Bleach's Thousand-Year Blood War storyline, Yhwach, the Quincy King, named five people who may change the course of battle before the invasion of Soul Society. Ichigo Kurosaki, Kenpachi Zaraki, Ichib Hysube, Ssuke Aizen, and Kisuke Urahara are the five "Special War Powers" (also known as "Special Threats").
Let's examine the justification behind Yhwach's choice to use cautious while dealing with these five unique dangers in Bleach, as well as whether or not they were as strong as their anticipated war potential.
Ichigo Kurosaki Consistently Outperforms Expectations
Ichigo's potential alone warrants his Special War Power designation. "Potential," here, refers not only to Ichigo's latent abilities but also his absurd growth rate, best demonstrated by his achieving Bankai in just two-and-a-half days, a feat requiring at least 10 years of practice for other Shinigami. Growth rate and potential also apply to Ichigo's combat sense, as he is quickly able to deduce enemy attack patterns and think up strategies on the fly. These qualities make Ichigo a wild card in the eyes of the Quincy, as time and time again he proves his ability to rise to the occasion and defy the odds, except when he fails his training for once in the anime adaptation.
Ichigo plays a pivotal role in the war itself. He saves Kenpachi Zaraki from a group of Sternritter ambushing him, thus preserving one of Soul Society's greatest assets, and most importantly, defeats Yhwach. This final confrontation is representative of Ichigo's potential at numerous junctures, as Yhwach notes that Ichigo's incredible growth is enough to change the futures that he sees through the Almighty.
Without being told, Ichigo deduces and capitalizes on Aizen's plan to deceive Yhwach using Kyōka Suigetsu, and after Uryū Ishida shoots Yhwach with the Silver Arrowhead, Ichigo evolves once again, as his Zangetsu reveals a second blade right as Yhwach destroys the first, allowing him to deal the decisive blow that saves the world.
In a fight, Kenpachi Zaraki is unmatched.
Kenpachi Zaraki was deemed one of the five Special War Powers due to his immense combat strength. Zaraki is the 11th Kenpachi, a title reserved for the strongest Shinigami in the Gotei 13, and earned by killing the current Kenpachi. A testament to his dual status as Kenpachi and Special War Power is the fact that he earned these distinctions before learning the name of his Zanpakutō and achieving Shikai and Bankai. Furthermore, Zaraki has not only defeated the 10th Kenpachi but, as a child, the 1st Kenpachi Yachiru Unohana as well. Frighteningly, in both these instances (and others), Zaraki was limiting his true power so that he could savor the fight, and still won.
In combat Zaraki is unmatched. Proficient in his own brand of swordplay, Zaraki can adapt his attack patterns with ease, and his ability to withstand his opponents' attacks while maintaining his offensive poise allows him to attack in situations where others opt to defend. He is so strong that Central 46 forbids him from learning Zanjutsu and studying proper swordsmanship under Yamamoto, as they fear a fully polished Zaraki going rogue.
Zaraki contributes heavily to the war effort. He assists in keeping Schutzstaffel member Gerard Valkyrie at bay after activating his Bankai, overpowering him before unfortunately succumbing to the strain of his newly untapped power. He also defeats the Sternritter Gremmy, whose power is literally imagination. The moment defining Zaraki's designation comes when Gremmy imagines his own strength as equal to Zaraki's, an action that results in his death as his body cannot handle power on par with Zaraki's.
Wisdom Makes Ichibe Hyosube a Superior Special Threat
Ichibē Hyōsube was selected due to his immense wisdom. Alive since its inception, Ichibē is the grandfather of Soul Society and within him lies its entire history and secrets. This level of knowledge grants Ichibē immense insight, allowing him to strategize and act from perhaps the most informed position of any combatant.
Unfortunately, this wisdom contributes to Ichibē's undoing. His eternal tenure as Soul Society's protector means that Ichibē witnessed the original defeat of the Quincy 1,000 years ago, a result that leads him to overconfidently believe that history would repeat itself. Ichibē does not account for Yhwach's ability to evolve, and as a result, suffers a crushing loss at the hands of the Almighty, far from living up to his estimated potential.
Known for His Spiritual Pressure, Sosuke Aizen
Sōsuke Aizen was placed on the list because of his immense spiritual pressure. Aizen's spiritual pressure was ridiculous even before fusing with the Hogyoku, exemplified by his negation of Soi Fon's Nigeki Kessatsu by simply overpowering her Reiatsu with his own. To fuse with the Hogyoku in the first place, Aizen states that Reiatsu at least double that of a captain level Shinigami is required, further stating that he is in possession of more than this amount in just his base form. After fusing with the Hogyoku, Aizen's spiritual pressure increases to a level that Muken cannot hope to seal, capable only of decreasing its area of effect.
Aizen plays a key role in the final confrontation with Yhwach. His Kyōka Suigetsu's complete hypnosis deceives Yhwach and gives Ichigo an opening to attack. The aftermath distracts Yhwach and grants Uryū Ishida the opportunity to shoot him with the Silver Arrowhead. As subjugation to an ability come down to the Reiatsu of one against that of another, the fact that Yhwach succumbs to Kyōka Suigetsu while merged with the Soul King demonstrates just how overwhelming Aizen is as one of Bleach's five Special Threats.
The Next Move of Kisuke Urahara Is Always Unpredictable
Kisuke Urahara was selected as a Special War Power because of his unpredictability. Deemed the "consummate schemer" by Askin Naak Le Varr, Urahara doesn't enter the fray unless he's prepared for situations A through Z and beyond. When Ichigo's Mugetsu failed to defeat Aizen it was Urahara that sealed him for good, revealing his creation of a Kido spell tailor-made for the occasion, a precaution that effectively saved the world.
In the war, Urahara's appearance is brief but impactful as he completely outwits Schutzstaffel Askin Naak Le Varr. After a one-on-one confrontation and at the brink of defeat, Urahara reveals his trump card: using his Bankai to create an opening in Askin's Gift Bereich that allows Grimmjow to enter and deal a fatal blow. When a dying Askin announces that his Gift Bereich will collapse and kill everyone present, we then see Nelliel Tu Odelschwanck, who reveals that this was within Urahara's foresight, stationing her to aid in his escape in case of such a turn of events.