Avatar: The Last Airbender (season 3)
This third and final season focuses on Aang's quest to defeat the tyrannical Fire Lord Ozai. In the season's beginning, protagonist Aang and his friends Sokka, Katara, and Toph are traveling through the Fire Nation, conjuring a plan for invading the Fire Nation and looking for a teacher to teach Aang Firebending. Midway through the season, Aang gathers friends he met in previous episodes and leads a failed invasion into the Fire Nation. Former antagonist and anti-hero Zuko changes sides and joins Aang, serving as his Firebending teacher until the season finale, when Aang finally defeats the Fire Lord and ends the war.