But that isn't what you were originally asking. My response addressed the points in your original post:
1. Yes, he faltered initially and drew on the dark side to try and attack the Emperor. But he backed away from it.
2. Yes, he attacked Vader in a rage and yes, he defeated him using the power of his emotions.
3. He stopped himself. He renounced that darkness and walked away from it. He failed to succumb in the end. And that is why the Emperor wasn't jumping with glee in the end. His laughter stopped because he SAW that Luke couldn't be turned. That the falter, even though it won the fight, was not going to dominate Luke's destiny.
Luke walked into the fire, he got burned, but he came out whole.
Only AFTER he won did he stop. If Vadar had defended that blow and nearly beat him. He wouldn't had the chance to do the right thing. He used the Dark Side of the force but as long as he does what is "right" in the end is all that matters.
Your first two sentences prove my point. He used raged/emotion those are Sith traits, whom is to say that if he would have been defeated he wouldn't have done what is right. Darth Vadar fought his master in a fury of rage. Yet he had been defeated which caused him to rage even more. As Darth Vadar was on the ground. He was screaming at his master "I Hate you"
In this situation. Luke Skywalker had defeated Vadar. My point is only that he used Sith Emotion/ Dark Side of the force. Only through the Dark Side was he able to defeat Vadar. You do not see Yoda or other Jedi using the Dark Side of the force. Why is it Okay for Luke Skywalker to use it, as long as he does what is right.
My overall point is proven that he used the dark side of the force to get victory, only through victory did he stop himself and go back to the light. Only when the rage had died down and he had obtained his goal. That is the point I am trying to make that he only was allowed victory by using his emotions/ dark side.
He wasn't able to defeat the Emperor using the light side or he would have never sliced Vadar in half had he not used his emotions only through that was he able to obtain victory. Using the Dark Side "at all" can have serious side effects. Why is okay for him to use the Dark Side, only when it suits him in direct conterdiction of his Jedi Teachings?
A: Would he have been able to defeat Vadar without using the Dark Side?
B: Did he indeed use the Dark Side to defeat Vadar. (Yes this was confirmed)
C: Why is it okay for a Jedi to use the Dark Side of the Force to obtain his goal as long as he uses the light side at the end.
I am hearing the feedback. I am not ignoring it. I would have expected more from someone who was trained directly by Yoda not to have been provoked. Using the Dark Side at all, usually leads to full dark side. That is my point. It's not the light that defeated Vadar. It was the dark side of the force.