I particularly liked the idea that Amon really knew energybending/spiritbending, because
(1) it was a new and spiritual bending technique that (according to Amon) normals could learn, and
(2) if you're familiar with wushia (kung fu) tropes, bad guys who know "good/light/pure" kung fu techniques (such as say secret shaolin chi) are especially scary. Kind of analogous to how Superman works so well as a villain. You kind of see this trope pop up in anime media, such as the final form of Kefka.