For Kenpachi, what kills him really does makes him stronger. It’s an interesting notion, and Kubo fleshes it out to explain a lot of Kenpachi’s battle history while Unohana kills him and resurrects him hundreds of times over. When they first met a very long time ago in Rukongai, it was their lust for battle and desire to find a worthy opponent that brought them together. Then because Kenpachi finally found a strong opponent, he unknowingly put limits on himself after that battle, which was what Unohana had hinted at in the previous chapter. The way I’m interpreting it is that because Kenpachi loved battle so much, he stopped fighting at his limit so that he could enjoy the feeling of fighting a worthy opponent again; if he unleashed himself, his subconscious fear was that his enemies would go down so quickly (as some of his lesser opponents already do) that it simply wouldn’t be “fun”. This explanation is in-line with his personality and history, and actually partially explains some of the inconsistencies in Kenpachi’s power levels throughout the course of the series. Unohana gives this as the reason why he lost against Ichigo, and why he only barely beat Noitora.
Unfortunately, this also means that Kenpachi is actually stronger than even Unohana, and as he is revived over and over again, his full potential begins to show and his strikes start to find their mark. Unohana takes a major hit at the end of the chapter, but despite the foreshadowing given in the past few weeks I still really do hope she survives. Kenpachi is great, but we’ve seen a lot of him already, and I’m more interested in seeing Unohana’s character fleshed out and developed beyond what’s shown in this battle – one that she has no intention of winning. Normally Bleach can be counted on for the good guys to survive crazy wounds, but those chances seem to be growing slimmer as Kenpachi grows more ridiculously powerful.