The Legend of Korra

Plot
The first season, Book One: Air, sees Korra move to Republic City to learn airbending from Tenzin, Avatar Aang's son. She joins a pro-bending team alongside the brothers Bolin and Mako, and befriends Sayo, heiress to a leading engineering corporation. The ambitious politician Tarrlok enlists Korra to fight the anti-bender uprising of the "Equalists", led by the masked Amon, who strips benders of their abilities. Korra and her friends, aided by police chief Lin Beifong, unmask Amon as a waterbender himself and Tarrlok's brother, ending the Equalists' coup.

In the second season, Book Two: Spirits, Korra's uncle Unalaq, chief of the Northern Water Tribe, seizes power in the southern tribe. While Korra's friends seek support against Unalaq, Korra learns of the first Avatar, Wan, who fused his soul with the spirit of light, Raava, to imprison Vaatu, the spirit of darkness. Unalaq frees Vaatu during the Harmonic Convergence, a decamillennial alignment of planets, and unites with him to become a dark Avatar. After defeating Unalaq, Korra chooses to leave open the portals between the material world and the spirit world, allowing a new coexistence of spirits and humans.

The third season, Book Three: Change, begins as nonbenders begin developing airbending powers as a result of Harmonic Convergence, and Tenzin, Korra, and her friends attempt to recruit them to re-establish the extinct Air Nomads. One new airbender is Zaheer, the leader of the anarchist Red Lotus society. The Red Lotus assassinates the Earth Queen, throwing her kingdom into chaos, and captures Korra to attempt to kill her and end the Avatar cycle. They are defeated by Korra's friends and the new airbenders, but Korra is severely injured and psychologically traumatized.

The final season, Book Four: Balance, takes place three years later. Korra slowly recovers from her mental and physical trauma. The metalbender Kuvira, assigned to reunite the fractured Earth Kingdom, declares herself head of the new, authoritarian "Earth Empire". Kuvira builds a spirit-powered superweapon and attempts to conquer Republic City. When Korra and her friends destroy the weapon, defeating Kuvira, the blast creates another portal to the Spirit World. The series ends with the prospect of democracy for the former Earth Kingdom, as Korra and Asami leave together for a vacation in the spirit world.