Itachi Uchiha is one of the most scariest as well as badass members of the Akatsuki. After all, he slaughtered his entire clan single handedly to test his powers. But again, how valid is the statement? rephrasing it, was there any other motive behind the slaughter? To find out, we need to understand the history of the Uchiha clan as well as Konoha
Who was Itachi Uchiha?
Itachi Uchiha was a true prodigy born to Fugaku Uchiha and Mikoto Uchiha. He experienced war at a young age. At the mere age of four, he witnessed the fourth great ninja war, which ultimately made him a pacifist. He knew the effects of war. The kind of impact it would have on people, property and integrity. He hated war for this very reason.
During the war, he tried helping a Hidden Stone shinobi who instead of accepting his help, tried to kill him. But he responded quickly with his kunai. He managed to protect himself, but grew curious over life, death and war. He approached Orochimaru for answers but the answer wasn’t satisfactory. He told him that life without eternity is meaningless.
At the age of 5, he met Shisui Uchiha who goes on to become his best friend. Shisui taught Itachi a great deal of things including life, war and hate. He along with Shisui took down members of the ANBU ROOT division without any trouble. It was genius at play. At the age of 5, he went on to graduate from the academy and was a Chunin by 7. He activated his sharingan by the age of 8. By 11 he was officially a member of the ANBU Black Ops.