Sara: That's not true. I wanted to kill Roy because that's what I do. That's who I am. I spent six years in the darkness and I looked into the eyes of the devil and I gave him my soul. Oliver: I can help you get it back. Sara: No. You deserve someone better. You can harness that light that's still inside of you, but I'm not that person and I never will be.
There is a prophecy. The man who doesn't perish at the blade of Ra'a al Ghul will become Ra's al Ghul. Ra's al Ghul doesn't offer, he orders. Oliver! Don't delude yourself into thinking you have a choice.