It's a basic principle of the universe that every action will create an equal and opposing reaction.

V (Hugo Weaving)

7 seconds sound clip from the V for Vendetta movie soundboard.

You can hear this line at 01:27:49 in the Blu-ray version of the movie.

Quote context

[...]

- No. She wrote the letter just before she died. And I delivered it to you as it had been delivered to me.

- Then it really happened, didn't it?

- Yes.

- You were in the cell next to her.

- And that's what this is all about. You're getting back at them for what they did to her. And to you.

- What was done to me created me.

- It's a basic principle of the universe that every action will create an equal and opposing reaction.

- Is that how you see it? Like an equation?

- What was done to me was monstrous.

- And they created a monster.

- Do you know where you'll go?

- No.

- That would have scared me before, but I suppose I should thank you.

[...]