Originally Posted by MammonAzrael
Extrapolating, had Luke given in to his anger, I could see Palpatine glorying in it, rubbing it in, and subduing Luke when he came to his senses. Then engineering his escape in such a way that he continues to take steps down the path to the Dark Side.
Except Luke did give into his anger, just that Vader blocked the lightsaber strike intended to kill Palpatine.
I don't think it's that well emphasised how close the Emperor came to turning Luke - it's only when Luke takes off Vader's hand that he finally comes to his senses.