And Naruto could not face his dark side until he was by that waterfall because every incident before that the Kyuubi took over so the sharingan not controlling sasuke's darkness is not an excuse really. The thing is Sasuke is already in control of his dark self
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Obito resisting the juubi proves that wrong.
Depends on how strong a will the user has.
If someone is consumed by hatred, like Sasuke before Vote2, than Sharingan wont save him.
His hatred was bigger than his willpower.
So yeah it depends on who is wielding the sharingan.
Besides I dont think that a sharingan would help much or maybe not at all in any of those scenarios.
The thing is Sasuke is already in control of his dark self.
Which Sasuke? Before or after Vote2?
What do you mean with ''in control of his dark self''?
The Sasuke before VotE2 was consumed by hatred. So in that sense he was not in control of the darkness in him. Meaning his will wasnt strong enough to overcome his hatred.
Thus hewould lose all the fights in the opening post. As willpower is the big factor there.
Shisui however could maybe handle the situations.
Obito still held on to bonds after all (still cared for example about the real Rin), which enabled him to not lose the willpower battle.
Sasuke wanted to get rid of all bonds.
If Sasuke was in control of the darkness in himself, than he wouldnt follow a dark path.
Being in control, as in, being able to prevent being consumed by it, by having enough willpower to resist the amount of darkness that you face.