was how bad they nerfed firebending. In the beginning, Aang accidentally scorched the skin off Katara's hands with basic practice fire bending techniques. Later in the series a direct hit basically amounted to a force push. Or an air push.
Remember that Aang, as the Avatar, is always going to be more powerful in his bending than others. Most firebenders do not firebend properly, using anger and aggression instead of the breath and the whole life-force aspect. Apparently only Iroh, Zuko, and Aang ended up firebending properly. Oozai and Azula were just naturally super powerful.
