Amon, also known as Noatak, was the leader of the Equalists, a group of chi blockers who sought to rid the world of benders and, in doing so, restore order and peace to the world.
 Skeletons in the Closet; Endgame
Unknown to his followers, Amon is a Water Bender and uses a rare form of Bloodbending acquired from his father to strip benders of their abilities. Avatar Korra reveals his true identity as Noatak to his followers at a rally and exposes his ability to bend. Initially, his followers reject the idea as Amon shows them a fake scar that he blames the fire nation to have created.
Amon catches up with Korra after she frees Tenzin and his family. He bloodbends Mako and Korra and proceeds to take their bending when his Lieutenant witnesses this and denounces him as a traitor. Amon bloodbends him, too, and strips Korra of her Water, Fire and Earth bending. Mako shoots him with lightning, giving them just enough time to escape. Amin catches up with the two but Korra surprises him with her newly found Airbending.
Amon is projected into the water, revealing his scar to be a false one. He uses water bending to flee when his followers see for themselves that he is a fake.
Amon catches up with his brother, Tarrlok, and asks him to escape with him. While fleeing on a boat, Tarrlok uses an Equalists Glove to cause an explosion. Despite not being confirmed, it is likely the two died from the explosion.