Eh, it's whatever. Itachi is the original Solo King. He has his own level and is OP in his own right.
In fanon only.
what? Sasuke is an Uchiha. The more hatred they have, the powerful their eyes become. Sasuke gained power because Itachi turned Sasuke evil. Sasuke should thank him
He changed Kabuto, turned him to the good side. Right now Kabuto can probably win the Gokage mid diff.
He stopped Edo Tensei, which played a big role in the beggining of the war(well until Itachi stopped it).
Sasuke was keen on taking revenge on Konoha, but after Itachi spoke to him, now he left obito and went against him. He wants to make his own village and doesnt want to destroy Konoha anymore.
Also Sasuke without Itachi's Mangekyo wouldn't be anywhere near the level he is at now, probably would be blind by now. Who does he have to thank? Oh yeah, thats right, Itachi =D
Are you serious? Itachi tortured and mind****ed his baby brother into a psychopath and ruining his life, told him to murder Naruto to get more power, and drove him into the arms of Orochimaru for more power (whom could had honestly just locked Sasuke in a cage and experimented on him until it was time to trade bodies if not for plot protection), and made Sasuke a missing-nin with an order of execution on his head and could had started a war between villages, and killed a respected Konoha elder.
Then, Itachi hoped Konoha would just welcome Sasuke back with open arms after everything. If Sasuke didn't return to Konoha on his own, his plan was to mind**** him again into a good guy... and still hope Konoha didn't kill him on the spot. Even then, Itachi was leaving Sasuke against Konoha, and if Itachi's plan worked and Sasuke got away from Tobi, Sasuke would had been killed during the Pein invasion.
And why did Itachi torture and mind**** Sasuke into a psychopath to begin with? So that Sasuke would kill him out of some sense of poetic justice.
Kabuto changed Kabuto, with incentive from Itachi; although that wasn't Itachi's original plan, rather it's something he resorted to because he was out of other options. Even when Itachi got Kabuto to undo Edo Tensei, all he really did was save the alliance from Kimimaro, a weakened Muu, and Chiyo without her puppets; all of the other Edo Tenseis were sealed already. He was basically a day late and a dollar short.
It was after Hashirama talked to Sasuke that he turned against Obito. Even after talking to Sasuke, he still intended on attacking Konoha, but wanted to get the whole story first since Obito lied about stuff. That's where the Edo Hokages come in, and that's when Sasuke changed his mind.
It's all Sasuke's power, don't kid yourself.