Pretty much this. If he had all Mangekyou Sharingan techniques (Kamui, Tsukuyomi, Amaterasu, Enton, Koto Amatsukami and Susanoo), he would've been far, far too much for his brother and would've easily kill him. Wouldn't you agree that these 6 skills are far too OP for anyone to possess all of them?If that's the case he would be untouchable O_O, i think he had a unique MS with unique abilities U_U