Ok some people either can't remember anything from the manga/anime or can't read! Everyone has full knowledge of itachi's abilities (no one knew this) and he knows theirs and he has NO ms. Therefore, itachi only easily defeats Kakuzu and Hidan as these two were only strong because their hidden abilities, but once you clock their abilities it's all over. Kisame would put up a good fight and could possibly win, unless Itachi is able to separate him and his sword, but Kisame has the advantage with his chakra, killer water techniques and speed. Now, Orochimaru is this fight also has the upper hand as each fight he had with itachi he was always caught by surprise, this is why itachi always bested him (including genjutsu). But if they both are full aware of each others abilities oro knows itachi's secret techniques and has the ability to resist his attacks better and I don't see itachi having a killer ass technique to actually KILL orochimaru and defeat all his counters. Deidara MAY have an advantage being that he is a long range fighter, and could keep his distance. Also he has that thing on his eye to detect genjutsu so an average genjutsu technique wouldn't work. Sasori vs. Itachi could go either way as I don't think genjutsu would have affected him in the first place (idk).