Knowledge?
Itachi vs Hidan: Hidan has shown to be stupid enough to fall for a "reality illusion" that Itachi could create while him watching thru his sharingan. Since Kisame wondered how the zombie duo died, it means that Akatsuki was well aware of Hidan's capacities and so does Itachi then. So in this case, while in the genjutsu, he would proceed to behead Hidan
Konan vs Itachi: This is a tricky match-up cuz Konan can multiply herself and spread all over the area and seems really intelligence and knowledgeable enough not to fall for a simple Sharingan genjutsu trick easily while fighting. So Itachi would have to force the eye contact, but because of Konan's property to cover and spread all over the area it would be difficult. We've already seen her capable to handling Jiraya's large katon attacks just fine, and herself can make explosive paper bomb clones. Because they are explosive tags(so no made of chakra), they are not easy to identify like we've seen during the fight against Tobi. So i hardly really see how Itachi wins this fight unless he somehow finds a way to put her in a paralysing genjutsu. The location in this fight will also be important
Deidara vs Itachi - Deidara has developed some counters to normal Sharingan genjutsu after his encounter with Itachi, so he won't fall for his genjutsu tricks, which is already a great advantage. The fact he is a long range fighter makes the thing even more difficult for Itachi since he has no long range attacks besides Susanoo. On the other side, Deidara could spam his clay bombs and unfortunately Itachi has no raiton affinities like Sasuke, so he couldn't stop the explosions by infusing them with raiton. So i don't see Itachi winning this match personally
Sasori vs Itachi - Genjutsu affects the brain, since Sasori is a puppet without brain, he should be immune to genjutsu. Sasori's arsenal is also really dangerous because with one hit, you get poisoned and it almost ends the match. With his wide range of poisoned kunais, hundred puppets, Sandaime Kazekage's jutsu, i don't think MS-less Itachi could handle it without protections like Susanoo or something else
Kakuzu vs Itachi - Kakuzu has great experience fighting even Hashirama, recognising the properties of the Sharingan by watching Kakashi, and knows Itachi in akatsuki, so i think he should be experienced enough to prepare himself in order to counter Itachi genjutsus capacity while fighting, and for that i think it should be better for him to leave some hearts inside him, while leaving others out. Because of the multiple chakra system, even if Itachi troubles one of them, normally the other one should be fine, which could help Kakuzu to fight as if nothing happened. Furthermore, we've seen that even after Kakuzu's death, the hearts are intelligent enough to act on their own, so it's definitely possible that they could disturb Kakuzu's chakra in this case. On the other hand, we've his doton defense that makes him immune to almost every physical attacks bar raiton and Itachi doesn't possess raiton techniques, so he doesn't possess the arsenal to break thru it especially without MS, when he would have to handle Kakuzu's multiple elements fire techniques, Kakuzu's fast tentacles difficult to predict, etc. So ultimately i give Kakuzu the win here as well
Kisame vs Itachi: Kisame is Itachi's partner in akatsuki since long time by now, so if someone should know almost everything concerning Itachi it should be him. So i think that he should know to fight Itachi without being caught by his genjutsu. Itachi on the other hand would have to try to forcibly put him in a paralysing genjutsu or something like this because besides it, he has absolute no way to defeat Kisame. And even so, we've seen Samehada able to act on his own and help his user if needed, so i think that if Samehada notices Kisame is in danger or being put in a genjutsu, it will either try to protect him or give him chakra to get out of it. Kisame's suiton > Itachi's katon. In the water dome, Itachi is also at a huge disadvantage. Kisame's Shark missile technique that absorbs every others. So i don't think he can defeat Kisame without MS either
