The Master
Zuko realised early in his travels that no matter if he succeeded or not, he would never amount to anything in his father's eyes. Instead he travels the world learning about other nations firsthand. He's visiting the south pole when Aang awakes and when they decide to go to the North Pole to learn waterbending, he asks to go with them. In time they learn that he's a firebender noble (he travels as an Earth Kingdom nonbender). In the North Pole Pakku refuses to teach Katara, so Zuko decides to try to use his firebending techniques to help her learn on her own, only using moon instead of sun, ocean instead of fire and focusing on her heartbeat instead of her breath. It works surprisingly well. Together they decide to try to convince Aang to leave the north pole and learn from Katara. Pakku is unimpressed by their decision to trust a girl who came there barely knowing how to bend with the Avatar's waterbending, until she uses his own saliva to make ice blades to chop off his moustache.