Did Sasuke kill Itachi?
Sasuke did not kill Itachi because at that point in time he was weak as compared to Itachi’s power level. Itachi is one of the greatest warriors who ever lived so how can he die so easily in a battle with his brother.
Itachi was very ill and he only kept himself alive for the sake of Sasuke. He wants to die from Sasuke’s hand so the Uchiha honor is restored and he also wants to teach Sasuke the powers of the Mangekyo Sharingan.
Itachi was nearly blind at the end of the battle with Sasuke. Plus he was blasted with drugs to just stay alive and well his disease was either something that wrecked his lungs or his heart.
In short, Itachi was not more Powerful than Sasuke at that time in fact he was at the lowest level of his powers. Even when Sasuke attacked him with the doctored shuriken he saw through it. Itachi used the Mangekyo and Amaterasu just to test Sasuke’s prowess.
Chakra exhaustion and using the Susanoo is also considered a reason for his death. The Susanoo is cited to be very chakra intensive and painful. Itachi needed to sleep to hold Ametarasu for a long time. His eyesight was blurred already. And Itachi also wanted to leave Sasuke his eyes so he could unlock the EMS.
We can say that Itachi was prepared for his death. He just wants to die for his village. Itachi wants to make Sasuke a strong weapon just like Minato died for naruto. So Did Sasuke kill Itachi Itachi? the answer is yes and no because Itachi wants to die by Sasuke’s hand therefore he was not fighting the battle honestly.