Voldemort didn’t break his promise to Lily—he intended to, presumably, but Lily broke her side first by trying to kill him instead of acting like a willing sacrifice.
First, I am certain that he completely anticipated her response. Desperate pleas aside, she wouldn’t have trusted that he would have really left Harry alive. He gave her a few seconds to think, come to that conclusion, and then she tried to the only option she thought she had left.
Second, the wording was:
“Very well,” said the voice of death, now sounding coldly amused, “I accept the bargain. Yourself to die, and the child to live. Now drop your wand so that I can murder you.”
The only part of the bargain that she had to uphold was dying.
Though I’m not at all certain that the scene is what it looks like.
Voldemort didn’t break his promise to Lily—he intended to, presumably, but Lily broke her side first by trying to kill him instead of acting like a willing sacrifice.
First, I am certain that he completely anticipated her response. Desperate pleas aside, she wouldn’t have trusted that he would have really left Harry alive. He gave her a few seconds to think, come to that conclusion, and then she tried to the only option she thought she had left.
Second, the wording was:
The only part of the bargain that she had to uphold was dying.
Though I’m not at all certain that the scene is what it looks like.