Because Itachi killed the whole uchiha clan and let saskje live. Im not gonna spoil the twist though
For revenge
sasuke is ashamed that naruto is getting stronger then him and the Orochimaru, Itachi thing "Because Sasuke wants to train with Orochimaru to become stronger and seek revenge on Itachi Uchiha."
Itachi didn't give his eyes to Sasuke. Itachi died in hand of Sasuke so Sasuke awakened Mangekyo Sharingan. Itachi still had eyes in his corspe when Madara took his body and Madara extracted Itachi's eyes which has now been transplanted to Sasuke recently. Sasuke now will have eternal mangekyo sharingan.
Sasuke kills him because of revenge after he find out the truth and regrets it
SPOILER ALERT!! Sasuke killed him to get revenge for Itachi
SPOILER WARNING!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!----------------------------------------------------------------------------------------------------------Itachi Uchiha killed Orochimaru. Some say that Sasuke Uchiha killed him, but technically, he didn't. Sasuke only consumed/took over Orochimaru. Then, in the battle between Sasuke and Itachi, Orochimaru came out of Sasuke, then Itachi killed him. Then, Sasuke Uchiha killed Itachi Uchiha
Sasuke already has a knowledge on why Itachi slayed his own family. He wanted to get revenge for the thing Itachi did, so in the end well if you don't know I won't spoil it for you.
To take revenge on him for making Itachi kill his own clan.
He goes after Itachi and gets his revenge but on the way was stopped by Deidara and Tobi (Madara).
actually, sasuke didn't kill itachi. when they fought itachi was hurt or sick, and he died. he never intended on killing sasuke. sasuke didn't know about itachi's past
When Sasuke was little he had a loving brother, Itachi. Itachi was forced to kill his clan, but he refused to kill his brother, the konoha elders threatened to start a war if he didn't. Itachi hated fighting but he was forced to and he pretended to be evil so his brother would be known as a hero one day after he killed itachi. Itachi never hated Sasuke , infact cared about him more than the village and his own life. After itachi lets sasuke kill him (although sasuke didnt know this.) Madarra told him why itachi assassinated the clan and that it was the senju's fault and selfishness. Now sasuke is filled with revenge and plans to destroy The hidden leaf village.
They took him so sasuke could take his eyes when he started to go blind.