Toph

Toph Beifong was among the most powerful earthbenders in the world. Toph was born blind, however, her blindness turned out to be a boon when she discovered the ability to "see" using earthbending to sense vibrations in the ground and discovered metalbending. Toph was also known as the "Blind Bandit" due to her prowess in underground earthbending competitions. She was initially disinterested in Aang's quest to save the world, but decided to join due to her overprotective parents, and became Aang's earthbending teacher.