Kisame Hoshigaki may have been a secondary villain in Naruto, but he was a major member of the Akatsuki until his final fall at the hands of Might Guy. When it comes to power, Kisame is likely stronger than practically every member of the Akatsuki, with the exception of the Djutsu users Itachi Uchiha, Obito Uchiha, and Nagato. This is due to his vast chakra reserves, superior expertise, and dominance of ninjutsu-based ninjas, which comprise the majority of Naruto's troops.
Kisame was significantly depleted and had degraded due to the nature of his mission during his infiltration on Genbu Island, hiding within Samehada. Despite being detected, he was able to escape Sage Mode's hands. Naruto Uzumaki, Killer B, and Yamato before being pursued by the sole ninja on the island capable of opposing him: Might Guy. If another ninja had pursued him, or if Guy had been replaced by a different Leaf Ninja Jnin, the outcome would have been very different.
Kisame Was Almost Unstoppable Against Ninjutsu Users
Kisame was vulnerable to Itachi and Obito because of their Sharingan. While the two Uchiha remained enormously powerful, it was their Djutsu and genjutsu that tilted the scales in their favour. Every single Akatsuki member would have been unable to outclass Kisame in taijutsu, or their ninjutsu would have been devoured by his attack, Water style: Great Shark Bullet. This is demonstrated by Kisame's rather loose treatment of Killer B, who could easily overcome Sasuke Uchiha, who had previously vanquished Deidara. Backtracking defeats and battles before Killer B reveals that Kisame was a tier above the rest of the Akatsuki.
As for the rest of the ninja world -- primarily those who could have been assigned Naruto’s support on Genbu Island -- none within the Hidden Leaf had the genjutsu skill to get around Kisame’s chakra-inhaling techniques, nor the taijutsu skill to counter Kisame’s own swordsman prowess. One of the reasons for Kisame’s defeat was not only due to power, but an incorrect decision. Kisame was primed and ready to handily defeat any ninjutsu thrown his way and incorrectly assumed that's what he would face.
Guy Was Kisame’s Perfect Counter in Naruto Shippuden
Only Might Guy's technique was a great counter to Kisame in the entire ninja world. Kisame's speed was comparable to Killer B, who equaled A's speed, but taijutsu speed alone was not enough to be Kisame's undoing. It was pure taijutsu force that could imitate ninjutsu. Guy's technique, Hirudora, was depicted visually as a ninjutsu, leading Kisame to believe that his chakra-stealing jutsu would absorb it and boost his own power. Unfortunately, the Monster of the Hidden Mist was incorrect.
Guy was still more strong than Kisame, possibly more powerful than any other ninja in Naruto (save the core protagonists), but if the events had played out differently, Kisame would have undoubtedly left Genbu Island and returned with crucial information for Obito. Having said that, it is unlikely that the ultimate war would have ended any differently if Kisame had survived and participated. Unlike the reanimations, Kisame would have been assigned to protect Kabuto as a living ninja rather than being thrown into the chaos of war.
