Kakuzu

Kakuzu (角都, Kakuzu) was an S-rank missing-nin from Takigakure and a member of Akatsuki who was partnered with Hidan. Kisame Hoshigaki jokingly referred to them as the Zombie Combo (ゾンビコンビ, Zonbi Konbi),^[2] due to the fact that, in a sense, they could not die. Within the organisation itself, Kakuzu acted as the organisation's Treasurer. 

Source: http://naruto.wikia.com/wiki/Kakuzu

Background

When under the servitude of Takigakure as an elite ninja, Kakuzu took on a mission to assassinate Hashirama Senju, the First Hokage. This mission, however, ended in failure due to the might of Hashirama's Wood Release techniques. Despite the insurmountable danger faced on the mission, what awaited his return to his village was the stigma and harsh punishment associated with the failure of his objective. In response to this treatment, a wrong levied against a shinobi who had put life and limb on the line for his village, Kakuzu came to hold a violent hatred for Takigakure as he escaped from imprisonment. In his flight from the village, Kakuzu killed the village elders, took their hearts, and fled with knowledge of the village's most prized forbidden techniques.^[1] He made a living off bounty hunting on the black market, and tearing out the still-beating hearts of powerful shinobi to extend his own lifespan and arsenal.^[3]
Some time after his defection, he joined Akatsuki, and was given a number of partners, most of whom he killed, due to his short temper. This is why he was eventually partnered with Hidan, whom he could not kill because of his immortality.^[4]
Also at some time in the past, he apparently encountered the Gold and Silver Brothers and witnessed Kinkaku's jinchūriki transformation.^[5]
In the anime, Kakuzu and Hidan met with Sasori and Deidara to discuss their new missions assigned by Akatsuki. After Kakuzu said they had a choice between a money-making mission and a war-mission, he chose the money mission after Sasori and Deidara showed no interest in it, much to Hidan's annoyance.^[6]

Personality

Kakuzu's money obsession.

Kakuzu was a greedy and miserly individual, arranging goals in terms of the highest profit he could gain from them, and was often unwilling to involve himself in something if there was nothing to gain from it, as well as claiming that he tended to forget opponents who were not worth any money after he was done with them. He even remarked that money is the only dependable thing in the world. Due to this end, he referred to himself as the "Treasurer of Akatsuki". Given his friendly relationship with Zangei, his bounty officer, it would seem he collected bounties rather frequently to earn cash, and did so (or at least tried) during his missions on several occasions. The frequent side-tasks and devotion to money were both major points of contention between Hidan and Kakuzu. He also seemed to respect an opponent who thinks well, as shown with his reaction to Kakashi's counters to Kakuzu's masks, and Shikamaru's quick analysis of Hidan's curse, even mentioning Shikamaru would have been a good bounty in the future.
Out of all the Akatsuki members, Hidan and Kakuzu displayed the most animosity towards each other, since neither of them were very fond of each other's interests. The two often traded barbs with one another, Kakuzu's usually having better timing than Hidan's. Hidan had shown great annoyance with Kakuzu's greed and occasional habit of doing or saying blasphaemous things, such as attacking a temple and killing the head monk for the bounty on the monk's head. Kakuzu, in turn, disliked Hidan's religion, believing the rituals associated with it to be a waste of time. Kakuzu was also rather impatient with Hidan's drawn-out speeches and battle style. Despite their mutual dislike of each other, their teamwork was almost flawless, because they complemented each other's abilities extremely well.

Kakuzu and Hidan in the midst of an argument.

The only reason that Kakuzu put up with Hidan was because he couldn't get rid of him. Due to his violent temper, Kakuzu often killed anyone close by when enraged. Hidan, therefore, was the perfect partner for Kakuzu, because of Hidan's inability to die. Kakuzu's somewhat indiscriminate attack style also made Hidan an ideal partner, since Kakuzu didn't need to worry about catching his partner in the crossfire.
Despite his obsessive personality and violent rages, Kakuzu was much more cautious than his partner, and was not as arrogant, never mindlessly rushing into battle like Hidan. Kakuzu frequently warned Hidan not to let his guard down, and then teased Hidan when he inevitably did. Kakuzu also seemed quite willing to follow orders. When ordered to retreat by the Akatsuki leader, Kakuzu complied immediately (while Hidan attempted to argue), despite the rather large bounty he could have received by taking Asuma. He seemed to forget the greater goals of the organisation when enraged, as he attempted to kill Naruto, in spite of Akatsuki's need to capture all the jinchūriki alive.

Appearance

Kakuzu.

Kakuzu was a tall, tanned, muscular man that towered over everyone in Akatsuki with the exception of Kisame Hoshigaki. He wore a white hood and a black mask, with his eyes being the only visible part of his face. Underneath, his mouth was stitched together at the edges (giving him a glasgow smile) and he had long dark brown hair. His eyes have an unusual colouring: green irides, no pupils and red sclerae. His clothing included the traditional Akatsuki cloak and the forehead protector of his home village with a scratch in the middle which symbolised that he was no longer loyal to it. He also wore dark red nail polish and his dark green Akatsuki ring with the kanji for "north" (北, hoku) was placed on his left middle finger. His entire body was covered with various stitches and predominantly appeared to be sewn together. This was a result of the unique technique that he possessed — the Earth Grudge Fear.
After being reincarnated by Kabuto Yakushi and restored by a talisman, Kakuzu gained dark grey sclerae, but retained his green, pupil-less irides. He no longer wore his forehead protector, hood or mask, causing his hair to be visible as it had been at the time of his death. He also no longer wore his vest, instead wearing a dark-red cloak with white lining, but still wore four masks on his back. In the anime, during the Chikara Arc, Kakuzu wore a black cloak with red lining in place of the cloak he would later wear.

Abilities

Kakuzu was a very powerful ninja, strong enough to become a member of Akatsuki. During his frequent rages, Kakuzu has killed many of his former partners in the organisation. A further testament to his skills was his survival in a battle against Hashirama Senju, despite ending up unable to complete his assassination mission. He had extremely high combat prowess and a vast array of techniques (due to his unique Earth Grudge Fear technique and near a century worth of experience). Those traits allowed him to fight several opponents while generally controlling the pace of the fight, including Kakashi Hatake with Chōji Akimichi and Ino Yamanaka as backup, and would have possibly killed them all, had it not been for the additional assistance from Team Yamato.