Board Thread:Theories and Speculation/@comment-31338621-20200901181802/@comment-32685487-20200903162832

You all must remember the novels are canon to the manga. Itachi only used Tsukuyomi with the intention to kill once and it drained his chakra more than it usually would because of that and he used it against a 3 tomoe Sharingan wielder(Izumi). He can definitely kill with it and make it much harder to break out of.. but the goal of the fight with Sasuke was to not kill him or mentally break him because Itachi was about to die and he had 2 goals he had to finish before he did(free Sasuke of Orochimaru's cursed seal, and awaken Sasuke's Mangekyo).