Korra

Avatar Korra, from the Southern Water Tribe, is the Avatar immediately succeeding Aang. She is a hotheaded and rebellious teenage girl. Being the manifestation of the planet in human form, Korra is the only living person who can bend all four elements.

Background
Korra was born in the Southern Water Tribe some time after the death of Avatar Aang. Much is unknown about her early life. However, it can be assumed that at one point in her life Korra learned that she was the Avatar, and began to train in order to become a fully realized one. Having already mastered Waterbending, Earthbending, and Firebending, Korra only needs to learn and master the art of Airbending and gain full control over the Avatar State in order to become a Fully Realized Avatar. About 70 years after the end of The War, Korra journeyed to Republic City seeking the tutelage of Tenzin, the son of Avatar Aang and Katara, as her Airbending master. During her travels, she discovered anti-bending unrest in the city. At some point, she gained an Animal Guide, a Polar Bear Dog named Naga and she will meet the sibling duo of Mako, a Firebender and Bolin, an Earthbender who will join her in the mission to rid the city of the Equalist Revolt.

Personality
Korra is fiery and pugnacious. Her personality in many ways is the opposite of Avatar Aang, her predecessor. Whereas Aang was a peaceful, nomadic Airbender, she is tough, headstrong, and combative. However, Korra also has a good sense of humor, with teenage charm and vulnerability.

Trivia

 * Korra is pronounced the same as the Irish word "cora" which translates as "weir."
 * Korra is also the name of a village in the Tibetan Autonomous Region of China.
 * Her name follows a long line of tradition in the polar Water Tribes, where often people include one or two "K"s and have an "UH" sound in their name (Katara, Hakoda, Sokka, Pakku, Kuruk, Kanna, Arnook, etc.)
 * Korra's situation appears to be the opposite of that of Aang; Aang had mastered Airbending and had to travel the world to learn the other three elements. Korra has mastered Waterbending, Earthbending and Firebending, and has yet to learn Airbending.
 * Korra is a word of Irish origin meaning, "from the mountain valley." It also means "crust" in Greek, and "grass" in certain Australian Aboriginal dialects and is an Estonian word meaning "procedure".
 * Korra's animal guide is a Polar Bear Dog called Naga.
 * Concept art of Korra shows her Firebending at a very young age. If true, this may explain how Korra has already mastered Earthbending and Firebending.