Originally posted by: CapsuleCorpJX
There is already at least one person stronger than Itachi:
Jiraya.
Maybe Tsuande.
The Third Hokage was also stronger, otherwise Itachi would have challenged him.

The last boss would be Kyuubi.
Itachi is the strongest character so far. Jiraiya is strong... but any technique he does will be copied, then countered or turned agaisnt him. Same with the 3rd, esp because of his age.

Tsunade isn't that great IMO. She is insanely strong... but thats about it. Itachi could outlast her, and if she was forced to use the seal on her forehead, she would kill herself.

Also, I still doubt that Kyuubi will be released... unless by another character. And how come people always classify them as "bosses"