Avatar Aang

Aang was an Air Nomad monk born in 12 BG and the Avatar during the Hundred Year War, succeeding Avatar Roku and preceding Avatar Korra. He was the youngest known airbender to receive the title of master, and also one of a select few Avatars, and one of the first in many cycles to learn the ancient art of energybending, and the first Avatar known to have actively used the technique.
Shortly before the beginning of the Hundred Year War, Aang was frozen in an iceberg for a hundred years; he later emerged, still biologically twelve years old, into a world engulfed by war. During his absence, the Fire Nation had waged war upon the other nations and managed to completely wipe out the pacifistic Air Nomads. He remained a kind and goofy kid at heart throughout his year-long struggle, despite the overwhelming loss of his people and the heavy burdens he was forced to bear.