In EP3 vader is very angry and full of hate even to Ben kanobi. Yes he is turning to the dark side but where is all that hate and anger gone in A NEW HOPE ?
because he's more machine than human (like OB1 said); he can't put much emotion in anything anymore
__________________ Kyuzo: Don't you see? A real sword will kill you. Mr. Earl Brooks: If I were here to kill you, you would already be dead. Mercedes: My mother told me to be wary of Fauns. Mr. Le Chiffre: No, I believe in a reasonable rate of return. James Bond: Now the whole world will know you died while you were scratching my balls!
3. Over 19 years, he still hates, but he's controlled it.
__________________ Recently Produced and Distributed Young but High-Ranking Political Figure of Royal Ancestry within the Modern American Town Affectionately Referred To as Bel-Air.
Registered: Nov 2007
Location: various remote midwestern hillbilly
Yeah, nobody can be at a full anger level for years on end. They are going to calm down pretty soon, even if there is still an underlying hatred that can surface easity. Imagine being as mad as you have ever been, and trying to stay that way for months or years on end. But he's still a pretty highly motivated-by-hatred kinda guy.
Registered: Oct 2004
Location: On cloud 9 in 7th heaven! I didn't
He could be constantly full of hate and anger... he's a Sith Lord. That's what fuels them. What separates them from the Jedi. He was probably more pissed that he was just bested by someone that he thought he was better than (and he was), and he realized that everything he sold out for was now pretty much done with, being as he was weakened. He was already remorseful for all he'd done, he just knew that he'd done too much to back. That's why he was crying on Mustafar.
But he just learned how to control his emotions rather than letting his emotions control him.