Here is a transcript of a lost scene from
The Empires Strikes Back
Darth Vader: Obi Wan never told you what happened to your father.
Luke: He told me enough! He told me you killed him!
Darth Vader: No, Luke... I am your father!
Luke: No. It can't be. That's not true. That's impossible!
Darth Vader: Search your feelings Luke... you know them to be true.
Darth Vader: Yes, it is true... and you know what else? You know that brass droid of yours?
Darth Vader: Yes... Threepio... I built him... when I was 7 years old.
Luke: No! ... Wait, huh?
Darth Vader: Seven years old. And what have you done? Look at yourself. No hand. No job. And you couldn't even levitate your own ship out of the swamp...
Luke: But... I destroyed your precious Death Star!
Darth Vader: But that was when you were 20! When I was 10, I single-handedly destroyed an entire Trade Federation Droid Control ship!
Luke: Well, it's not my fault...
Darth Vader: Oh, here we go... "Poor me... my father never gave me what I wanted for my birthday... boo hoo, my daddy's the Dark Lord of the Sith... Nobody loved me... waahhh wahhh!
Luke: Shut up!
Darth Vader: You're a slacker! By the time I was your age, I had already exterminated the Jedi knights!
Luke: I used to race my T-16 through Beggar's Canyon.
Darth Vader: Oh, for the love of the Emperor... 10 years old, winner of the Boonta Eve Open... the Only human to ever fly a Pod Racer... right here baby!
Luke looks down the shaft. Takes a step towards it.
Darth Vader: I was wrong... You're not my kid... I don't know whose you are, but you sure ain't mine.
Luke takes a step off the platform, hesitates, then plunges down the shaft.
Darth Vader looks down after him.
Darth Vader: And get a haircut!