Wow its crazy how on the base, Itachi is on a high ass pedastool. Yea he would win but he has only a 51 percent chance meaning the battle can come down to a variety of things such as Kisame's level of seriousness, if he starts of with fusing with samehada and then use that water dome and it then drain Itachi of his so little chakra then probaly but like I said its a win for Itachi.