Noatak was a good-natured kid. He is the firstborn of the Yakone family. He was a kind person and wanted everyone to be treated fairly and equally. When his waterbending skills come out, his father took him on a hunting trip with his brother (Tarrlok).
Noatak was a very skilled bender, he was perfectly bloodbending. He's a prodigy, mastered Yakone's psychic bloodbending technique by the time he was 14. But he changed during his bloodbending training. He became cold and detached. One day, his father wanted to bloodbend his brother and he bloodbend him without hesitation. When his father abused Tarrlok, he get mad and bloodbend his father too. Then ran away from his family.
The Equalists/Becoming Amon
Noatak wanted everyone to be equal, and he decided to destroy the benders. He developed a new technique. With his new technique, he can take away a person's bending skills (like energybending). He decided to start a revolution
During the Air Book, he was disclosure by Avatar Korra. When everyone found out he's a bender too, his comrades stopped supporting him. Noatak died with his brother in a boat explosion.