Itachi Uchiha

is a missing-nin from Konohagakure and is partnered with Kisame Hoshigaki. He is one of only 3 surviving members of the Uchiha clan. (Itachi convinced Sasuke to activate the Mangekyo Sharingan, stating that if he did, there would be three MS users. The second MS user is unknown, but it is speculated that it may be Tobi; since he has recently revealed himself to be Madara Uchiha, and besides the fact that he had revealed his regular Sharingan at the same time, Kyuubi had mentioned Madara's eyes to be extremely sinister. Since Madara Uchiha is supposed to be the founder of Uchiha, it would make sense that he had invented the Mangekyo Sharingan as well.)

History
During his time in Konoha, Itachi's prodigious talents and rapid development into a skilled ninja earned great attention from his family, the Uchiha clan. His skills were such that his family focused all of its attention on him and the prospect that he would be the clan's future, ignoring Itachi's younger brother Sasuke Uchiha in the process. Over time Itachi began to distance himself from the village and his family, eventually becoming a prime suspect in his best friend, Shisui Uchiha's, death. Before the death could be properly investigated, Itachi killed all the members of the Uchiha clan in a single night so that he could "test [his] ability". Itachi decided to spare Sasuke, however, feeling he was not worth killing; instead, prior to leaving, Itachi told Sasuke to live hating him and get strong enough to avenge the clan. At some point in time Itachi joined Akatsuki. While it stands to reason that he joined after massacring the Uchiha clan, the timeline that has been given throughout the series coupled with his age suggests that he joined the organization prior to killing his clan.

Fighting Style & Abilities
Although he is a member of Akatsuki, Itachi does not find great interest in fighting. He instead prefers to avoid battle or, if that is not possible, end it as quickly as possible while exerting as little effort as he can. When he does fight Itachi remains stationary, attacking only in defense and to otherwise avoid damage. He also studies an opponent's movements with his Sharingan eyes, using them to properly assess an opponent's actions and respond accordingly. His Sharingan is further enhanced when he activates his Mangekyo Sharingan, the strongest ability a member of the Uchiha clan can gain, which he acquired after he killed Shisui Uchiha. With the Mangekyo Sharingan Itachi is able to utilize attacks that can defeat even the strongest opponent, though it has been suggested that he is losing his eyesight as a result of repeated use. In addition to his Sharingan-based abilities, Itachi is very skilled with genjutsu. Itachi is so skilled with genjutsu that he can trap others with illusion by merely pointing or looking at them, as well as turning their own genjutsu against them without their notice. His most notable ability is a Genjutsu (Tsukiyomi) that is impossible to dispel, a technique that can completely submerge the victim in to a parallel world where time is perceived as much slower, and instant in the real world is worth 24 hours in this parallel dimension. The World of the Grasping Moon, as Itachi calls it. What makes this technique efficient in battle is his ability to do whatever he wants to his victim, from forcing him to relive moments of his life, to complete torture.