How we cite our quotes: All quotations are from Star Wars: Revenge of the Sith.
Quote #10
ANAKIN: What have I done?
PALPATINE: You are fulfilling your destiny, Anakin. Become my apprentice. Learn to use the dark side of the Force.
ANAKIN: I will do whatever you ask.
PALPATINE: Good.
ANAKIN: Just help me save Padmé's life. I can't live without her. I won't let her die. I want the power to stop death.
PALPATINE: To cheat death is a power only one has achieved, but if we work together, I know we can discover the secret.
ANAKIN: I pledge myself to your teachings. To the ways of the Sith.
PALPATINE: Good. Good. The Force is strong with you. A powerful Sith you will become. Henceforth, you shall be know as Darth … Vader.
This is the moment when Anakin finally, consciously decides to switch sides in the battle between good and evil. Up until now, he's fought against the dark side, and his inner urges, in the quest to remain a good Jedi. But now he's desperate, and he's willing to do anything to save his wife.
Quote #11
PALPATINE: We must move quickly. The Jedi are relentless; if they are not all destroyed, it will be civil war without end. First, I want you to go to the Jedi Temple. We will catch them off balance. Do what must be done, Lord Vader. Do not hesitate. Show no mercy. Only then will you be strong enough with the dark side to save Padmé.
Yeah, OK, that makes sense: go do something really, really bad in order to get stronger—but we're definitely the bad guys.
Quote #12
ANAKIN: If you're not with me, you're my enemy.
OBI-WAN: Only a Sith Lord deals in absolutes. I will do what I must.
Once again, in the quest to label one side good and one side bad, the world becomes pretty black and white. (And, by the way, this line cracks us up. "Only a Sith Lord deals in absolutes" is an absolute statement.)