Complex sentence: Although Ozai is subdued, Aang refuses to kill him; instead, he locks down Phoenix king Ozai with earth, and he realizes what the Lion Turtle had meant and uses Energy bending to strip Ozai of his Firebending powers, ending his ability to wage war.
Split into simpler sentences: Although Ozai is subdued, Aang refuses to kill him; instead, he locks Ozai down with earth. He realizes what the lion-turtle had meant and uses Energybending to strip Ozai of his Firebending powers, ending his ability to wage war.