Board Thread:Versus Debates/@comment-37265641-20181022021850/@comment-32685487-20181125003535

Kisame said himself Itachi is stronger than him, and if Kisame himself expresses that confidence then that's a fact. Kisame was even sure that Itachi could beat Jiraiya AND the Jonin and confused as to why they were fleeing instead.

and no, Itachi cannot beat Kaguya unless he gets lucky and lands the SoT. NOBODY can beat Kaguya unless they have the SoT or Six Paths Chibaku Tensei. She is literally the strongest thing there is in the Narutoverse as of yet.