DominicCobb said:
Luke throwing down his lightsaber might be the best part of ROTJ. He's finally learned the lesson from the cave. "I am a Jedi, like my father before me." Chills.
Pretty much this ^.
Luke doesn't even now what it is to be a Jedi before that moment (Or what the darkside is). Then throwing down his sabre he finally gets it. In that moment he has just tasted the power that the dark side would give him and yet still rejects it. The Emperor also recognises this and admits defeat.
ROTJ hands down beats ROTK on this front because Frodo never has that moment where he conquers the dark power of The Ring. It just goes down to a twist of fate.
Luke's plan was just to try to turn his father back to the light. He didn't understand how he'd be tested, so he had no plans beyond that.