A genius above all others, Itachi was born into the Uchiha Clan and praised by all as the best of his generation. However, not even his family, friends, or teachers could understand him.
Not much is known about Itachi's childhood, only that at age 4 Itachi had already witnessed countless lives lost due to war, which emotionally traumatized and effected his demeanor. It is also known that he graduated from the ninja academy after only one year. At age 7 he graduated from the Academy and mastered the Sharingan at age 8, passing the Chunin exam at age 10 and becoming ANBU Captain at age 13.
He was praised highly by his father, who saw the family's future in Itachi and neglected his other son-- Itachi's little brother Sasuke. However, during this time Itachi showed great affection towards Sasuke, and even encouraged his father to come to the Academy when Sasuke was enrolled, something their dad had otherwise forgotten, by saying that he would otherwise not come on a mission.
After having acted strange for a long time, not coming to the clan meetings and refusing to train with Sasuke, it would finally seem that he snapped. With the help of Madara's teachings (and possibly the help from Madara himself), he slaughtered his entire clan overnight(with the exception of Sasuke). Due to the fact that Sasuke was never to know about the Uchiha's attempt at a coup'd etat and the Konoha higher ups's orders, Itachi used his Mangekyo Sharingan to capture Sasuke in a genjutsu and show him how he had killed everyone. After this Sasuke ran away, but Itachi confronted him again and explained that he did it all to test himself. He also explained that the new eyes he had acquired could also be acquired by Sasuke and all he had to do was to kill his best friend. Telling Sasuke that he let him live because he had the potential to become as strong as him, he also tells him to hate him and detest him, if he ever wanted a chance of defeating him.
In the few battles he has been seen in since the start of the series, Itachi was shown as a very powerful ninja. This is demonstrated by his ability to easily defeat Deidara and Kakashi Hatake. It was also revealed that Itachi is the man who made Orochimaru leave Akatsuki, but not before severing his hand as punishment. Also, even after the two and a half years of hard training he received from Orochimaru, Sasuke and Itachi's match ended in a stalemate even though Itachi was not fighting at his full capabilities (he was later revealed to have had a serious disease that required medicine to keep him alive.) He's the strongest genjutsu user seen so far in the series. He is a master of the Sharingan, as he has demonstrated great talent with its abilities, such as its unique genjutsu throughout the series. When faced with an opponent's genjutsu, Itachi can use his Sharingan to dispel it or perform "Demonic Illusion: Mirror Heaven and Earth Change" and turn the Genjutsu against its user. Itachi is also noted to be very fast with his movements, since Kakashi, a fellow Sharingan user, couldn't keep up with his speed.Sasuke later commented on this speed in Part II during his fight with Itachi, since Itachi was capable of forming hand seals while throwing multiple shuriken and defending Sasuke's attacks at the same time.
Itachi also possesses the Mangekyo Sharingan, which enables him to use his most powerful techniques. With his left eye, he can use Tsukuyomi, a genjutsu that traps an opponent's mind in an illusionary world, torturing them for what seems like days in a matter of seconds. With his right eye he can use Amaterasu, which allows him to create a black flame that he can direct with his eyesight, burning everything in its path. His final technique is Susano'o, a technique that manifests as a spectral being made of chakra resembling a yamabushi with a tengu mask surrounding his body. It wields the Totsuka Sword, a spectral sword with the ability to bind what it cuts into an alternate dimension, trapping it in a Genjutsu state forever, and Yata's Mirror, a shield that can reflect many attacks. Zetsu, a fellow Akatsuki member, states that Itachi's mastery of the Sharingan's Eye Techniques and genjutsu makes him invincible to many opponents. Despite his mastery of the Mangekyo Sharingan, Itachi is falling prey to its side effects, as his eyesight is worsening after every activation and he will eventually go blind from its power, and his Sharingan will be forever sealed away.
In terms of standard Ninjutsu, Itachi can create Shadow Clones to perform techniques for him and act as shields from attacks. These clones can also be commanded to explode with "Clone Great Explosion" .As a member of the Uchiha clan, he can also perform "Fire Release: Great Fireball Technique" to catch opponents in a blast of fire, and in the anime can breathe multiple fireballs with Fire Release: Phoenix Immortal Fire Technique . With "Water Release: Water Fang Bullet" he can also catch targets in a circle of crushing water.
This is Itachi Uchiha....
Itachi's Sharingan-mangekyou....
