If he born in the war time, I believe he can be a totally hero to Konoha: Graduated from Ninja school in seven years old; open his Sharingan ability in eight years old; become a Chuunin at ten;
become the youngest Anbu leader when thirteen years old. A really genius and hero to the whole world even though almost everybody treat him as a evil!
After accept the order of third hokage, Itachi decided to be a devil and killed almost everyone of his family except his little brother Sasuke. He know this is the best choice, sacrifice himself to avoid a war, but he cannot kill Sasuke because he has no fault. Itachi join in the Akatsuki after this affair and change into a undercover in this organization/ Seems that he know something about Pain and Madara, he use his special way to protect Konoha, Sasuke, and in order to make Sasuke more stronger, he planned a conflict with him. And play a evil role until his dead, leave a hope to Naruto and want to bring Sasuke back to Konoha.
We have no doubt about Itachi's power. When he still alive, Madara cannot do any big actions to the Ninja world. He can beat horrible Orochimaru in a seconds. Just use his vision almost killed Kakashi in Konoha. Escape from the Ninjutsu of Jiraiya. Training Sasuke more powerful when he was illness and send his Sharingan to Sasuke finally dead. He is a darkness hero and I believe everyone should show respect to him!