Please. Six Paths at once, Gedo Mazou, Chibaku Tensei, Asura Path spamming bombs and lasers, Large-Scale Shinra Tensei, barrage of summons>Itachi.
Gedo is powerful, but an easy target. Totsuka blade one shot seal. Amaterasu one shot burned.
Chibaku tensei. It is unknown whether or not his long rage move by its self could have destroyed it, but it is possible. Regardless if he knows about chibaku tensei, he won't get allow him to do it.
Asura path is nothing, Itachi is able to move extremely quickly and can dodge the most intense attacks easily.
Large scale shinra tensei leaves the deva path unusable for a certain length of time. Blocks it with yata mirror and makes him waste it.
Birrage of summons? Totsuka sword seals them or he fodderizes the summons like he did in the fight with nagato.
You tell me how Nagato will get past all of Itacih's genjutsu, sussano with yata mirror+totsuka sword+magatama, and amaterasu.
Amaterasu immediately takes out 4 of the six paths of pain. The only ones that can survive it are preta path and deva path (if he can use shinra tensei to blow them away before hes burnt), while preta path is absorbing it, totsuka sword. Boom down to 1 left. And the deva path who is extremely badly burned is nothing in front of the eyes of Itachi.
Edit: @ Sir Blades of chaos : Oh no, ouch that stings. A person on the internet called me stupid with a picture.