It's Itachi for me, he didn't lose to Sasuke when they fight Itachi just wanted to remove and seal Orochimaru from Sasuke's body and if Itachi fight in his full potential strength Sasuke would be dead.Who is the most reliant character in naruto? Reliant includes mostly winning by ocular powers, biju etc.
Um the reverse genjutsu he used on kurenai, the genjutsu he caught Bee in, the genjutsu he caught Naruto in, the genjutsus he caught Sasuke in before he used Tsukuyomi, the genjutsu he used on Oro (maybe, we don't know).Itachi namikaze, what gen does itachi have without sharingan?