Based on a manga by Shindou L.

Who killed Kisame in the Naruto anime?

*SPOILER ALERT ⚠ * At first kisame was thought to be dead when bee took samehada from him and bee and his brother, raikage doubled up on him and decapitated him using double lariat. Zetsu later revealed that the decapitated body was one of his clones, which switched with Kisame when B obscured the water dome with his ink, and that the real Kisame was hiding inside Samehada in order to infiltrate Kumogakure.
The sword itself was taken by Killer B, who planned to use it as his new weapon.
Here is a picture of kisame hiding in samehada. After B helped Naruto to tame the Nine-Tails, Naruto was able to sense Kisame's hatred within Samehada, despite his and Samehada's identical chakra.
Discovered and outnumbered, Kisame took Samehada and tried to escape, but Naruto used the new speed granted to him by the Nine-Tails to stop him.
He still ran away but was countered by guy on the way. Kisame then used Water Release: A Thousand Feeding Sharks to conceal it and overwhelm Guy.
When Guy's Morning Peacock couldn't destroy all of the sharks, he opened the seventh chakra gate, blocking the sharks' route.
To get rid of Guy, Kisame used Water Release: Great Shark Bullet Technique, and Guy countered with his Daytime Tiger.
Although the Great Shark Bullet grows stronger when used against chakra-based attacks, Daytime Tiger was composed of "youthful" air pressure.
It overpowered and defeated Kisame, as well as destroyed all of the remaining sharks.
Though defeated, Kisame was annoyed that Guy still could not remember him and tried to continue fighting, but was knocked unconscious by Guy. He was captured and team of Yamato and ao tried to read his mind but he bit his own tongue and tried to be free.
The Kumo and Konoha-nin tried to subdue him, but Kisame trapped himself with the Water Prison Technique.
Before he was completely immobilised, he summoned three sharks and allowed them to devour him.he ended his own life with a smile thinking about his friend itachi which gained his respect from guy. As a testament of their long-time bond, Samehada cried for Kisame when its former master killed himself.
Upon seeing Samehada in Killer B's possession, a reincarnated Itachi instantly realised that his former partner had died.
He was a legend of his ownown.
Hope this helped. *loki out*!