Who is the strongest soulreaper in bleach?!
Question: Zaraki Kenpachi
Answers: Zaraki Kenpachi
In terms of brute strength: Zaraki Kenpachi
In terms of techniques, skill, and speed: Kuchiki Byakuya
In terms of natural talent: Kurosaki Ichigo
Sōsuke Aizen is the stongest Shinigami in Bleach. That's not based on my opinion. That is who has been shown to be the strongest. But they have not shown the full powers of some of the other Captins, like the Captin of Squad 1, Shigekuni Yamamoto-Genryūsai, who is said to be the strongest of all Captins in the Gotei 13. But so far, Aizen is the strongest. They have not really shown his power yet either, but he has hit the limit of power a Shinigami can reach. Captin Tōshirō Hitsugaya had trouble with one of Aizen's Arrancar. But most of the Arrancar and Shinigami under Aizen talk like Aizen is a God. For that many strong shinigami/hollows to follow Aizen without turning on him must mean Aizen is very strong. But I'm sure someone will become stronger than him sooner or later.
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It's without a doubt Aizen. There's a reason some people have nicknamed him "Captain Broken". His Shikai hypnotizes anyone who sees it, allowing him to control everything they see, and this effect apparently never wears off. So if you *ever* see him use it, he pretty much owns you. It's similar to the Mangenko Sharingan, except that he can position it anywhere near himself, so you can't look at his feet to avoid it, and he can hit everyone within sight with it simultaneously.
And that's just his Shikai. He also has a Bankai we haven't seen yet. We know he has it though, since it's said that all captains besides Kenpachi have one, and Aizen at one point says his Bankai is not something that should ever be used when sparring. What can be more powerful than an ability that is instant win?
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