well your still close but he did kill his best friend before he killed the clan because they had enough time in between to confront him about where he was and if he knew what had happened to Shisui Uchiha. They knew he had killed him but couldn't prove it so they tryed to force him to admit to it. later on he decided he wanted to test the abilities of it and what better way to find out how much more powerful it was than to go against an entire clan with the sharingan.
itachi killed his clan because he was testing his abuiltes or to mess with yonger brother or he was just crazy. i think its a mix of all three and itachi crualness. i mean look at his eyes he has no soul. he probably used a jutsu[forbidden] to dispose of it.
He killed them so he could test his skills he says so right on one of the episodes he kills his friend for that power eye thing.
look guys is really easy and complicated all @ the same time. Itachi killed his clan to know how many sharingan users he could kill without his real bloodline limit runing out and you gus remembered what happened to kakashi when he got caught in that sharingan. He couldn't move a muscle and it felt as if he had been tortured for years whern it wasa only a few seconds so the same thing could have happened to his parents and clan members and also he left sasuke alive because he wasn't even going to waste chakara in smashing a bug or it could be that he left him alive so that he could unlock the greate power within him that would be awakened with hate :mad:ALSO HE KNEW THAT SASUKE WAS CABAPLE OF GREATE THINGS AND THAT HE (ITACHI) HAD DONE A BIG MISTAKE SO HE FINISHED IT OF AND LEFT HIS LITTLE BRO ALIVE BECAUSE HE ALWAYS PROTECTED HIM NO MATTER WHAT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:mad:!!!!!!!!!!! !!!!!!!!!!!!!.
I appreciate the time you heve taken to read this thank you and have a nice day.;)
Itachi left his brother hoping that Sasuke would get strong enough someday to give Itachi a great fight and make Itachi have to reach his limits. Itachi killed his clan to see if it would be a challenge. He had been the golden child since he was born, and he got bored. He needed a challenge. I do not thing Sasuke alone will be able to kill Itachi. In the end I think Itachi will sacrifice his life to Sasuke to keep him from turning evil by the power of the Uchiha clan. It is rumored that the true dark power in the Sharingan could match that of the nine tailed fox. I really want Itachi to be evil, makes a better story line, but something tells me he will do something good in the end.
they probably regreted leting itachi live but realized it before it was to late. i mean itachi killed all of is family to put and end to uchiha blood line. he probably meant it as a good thing. weird huh? he probably knew all of the power the sharingan possed and wanted it to end. he may not have killed saskue because he was so tormented and emotionly full he couldn't. i mean with all that killing wh wouldn't break down. *depressed face* xoxoxo