Amaterasu

Amaterasu is the highest level Fire Release technique, and according to Zetsu, one of the most powerful ninjutsu in existence. It is said to represent the, the antipode to Tsukuyomi, a genjutsu of similar power and a fellow Mangekyō Sharingan dōjutsu.

The jet-black flames of the Amaterasu, said to be the fires from hell that are as hot as the sun, ignite at the focus of the user's vision. Though boasting unavoidability, Amaterasu has been avoided a few times; Sasuke Uchiha managed to dodge the flames Itachi tried focusing on him, though Itachi did not actually want to kill him and managed to hit Sasuke shortly after regardless, and A using his Lightning Release Armour avoided a short-range Amaterasu launched at him by Sasuke. The determining factors seem to be motivation and skill of the user, and the speed and experience of the target.

The flames are capable of burning through anything in their path, even smothering regular fire techniques with ease. Amaterasu is said to never stop burning until whatever is caught by the Amaterasu is completely reduced to ash or destroyed. It cannot be extinguished with water or any other normal methods. The only thing the the flames have failed to burn into is Gaara's chakra infused sand. However, the flames burn fairly slowly, allowing anyone struck by Amaterasu an opportunity to remove whatever clothing or body parts have been caught ablaze. Use of the technique also puts a great deal of strain on the user, usually causing their eyes to bleed.

Amaterasu was originally unique to Itachi Uchiha, who used it with his right Mangekyō Sharingan. He was able to quell the flames to some extent. Prior to his death, Itachi implanted some of the black flames into Sasuke's eye which activates upon seeing Madara Uchiha's actual face. Sasuke, after gaining his own Mangekyō Sharingan, is later able to use Amaterasu on his own. Sasuke's Amaterasu originates from his left eye, and C indicates he is more skilled with it than Itachi; he can put out the flames with greater ease and speed can even manipulate the flames themselves into different shapes for attack and defense as part of his "Blaze" element.

Influence
As from the ancient Japanese myth and religion of Shintō Amaterasu, Tsukuyomi, and Susanoo are all gods. When Izanagi washed his face after escaping the underworld his left eye became the Sun Goddess, Amaterasu.