[X] A lightning bolt. With Mai and Ty Lee there to keep Zuko's second in check, for the first time you may well be able to have a genuine Agni Kai. Just you, and Zuko, and the flame. The way it really was meant to be. And when you win—well, he'll probably have the waterbender there to heal him, and then you can talk, once your claim is so secure even the Avatar can't dislodge it.
I think this is the best choice. Let the girl have her one victory over zuzu and than Azula can tell him how she's the best