Misinterpreting the ending of that fight is a common thing, I think. Itachi didn't actually kill Sasuke. Not physically, anyway. The whole point of their final battle was to end the curse of hatred Itachi had placed on his brother, not to take his life. He was literally on his deathbed, fighting to push Sasuke to his absolute limit to exhaust Orochimaru's influence and then seal him away with the Amaterasu trap. Calling it 'killing' misses the agonizing, decades-long emotional choreography Itachi was forced into. He spent his entire life after the massacre making sure Sasuke would survive to be the one who killed him, the villain. The ultimate failure would have been Sasuke dying in that fight. Itachi orchestrated everything so his brother would walk away with the power and the narrative of the victor, even if the cost was incomprehensible.
That Amaterasu trigger wasn't a murder attempt; it was a final, posthumous protection against Obito. Itachi knew he wouldn't live through the battle, so he left a 'gift' programmed to activate if Sasuke ever saw Obito's Sharingan. Every single action in that encounter was a sacrifice wrapped in another layer of brutal, loving calculation. He died giving Sasuke his eyes, for god's sake. The tragedy isn't that he tried to kill him, but that he had to make his brother hate him enough to become strong, all while secretly planning to be the final stepping stone in his path.