Star Wars Episode VI: Return of the Jedi1983

[Yoda has passed into The Force, Luke is sitting outside his hut with R2]

Luke:
I can't do it, R2. I can't go on alone.

Obi-Wan Kenobi:
[voice emanates from nowhere] Yoda will always be with you. [reveals himself as a spirit walking nearby]

Luke:
Obi-Wan! Why didn't you tell me? You told me Vader betrayed and murdered my father.

Obi-Wan:
Your father was seduced by the dark side of the Force. He ceased to be Anakin Skywalker and became Darth Vader. When that happened, the good man who was your father was destroyed. So what I told you was true, from a certain point of view.

Luke:
[incredulously] A certain point of view?

Obi-Wan:
Luke, you're going to find that many of the truths we cling to depend greatly on our own point of view. Anakin was a good friend. When I first knew him, your father was already a great pilot. But I was amazed how strongly the Force was with him. I took it upon myself to train him as a Jedi. I thought that I could instruct him just as well as Yoda. I was wrong.

Luke:
There is still good in him.

Obi-Wan:
He's more machine now than man. Twisted and evil.

Luke:
I can't do it, Ben.

Obi-Wan:
You cannot escape your destiny. You must face Darth Vader again.

Luke:
I can't kill my own father!

Obi-Wan:
[resigned] Then the Emperor has already won. You were our only hope.

Luke:
Yoda spoke of another.

Obi-Wan:
The other he spoke of is your twin sister.

Luke:
But I have no sister.

Obi-Wan:
[nods] Mm. To protect you both from the Emperor, you were hidden from your father when you were born. The Emperor knew, as I did. If Anakin were to have any offspring, they would be a threat to him. That is the reason why your sister remains safely anonymous.

Luke:
[with sudden realization] Leia! Leia's my sister!

Obi-Wan:
Your insight serves you well. Bury your feelings deep down, Luke. They do you credit, but they could be made to serve the Emperor.