nah i think itatchi didn't really want to kill the whole clan, i do believe someone else is behind it besides itachi or maybe he was force to kill his family or else a bad villian will do it themselves. its really hard to believe itachi is born pure evil after parents love him so much...and leaving sasuke to test his strength really didn't make sense, y dont anyone jus kill him if he wanted to be the strongest, or why would he join the akatsuki clan and why not kill everyone in the akatsuki clan to test his strength...i do think there is a great evil power that didn't explain yet...