Avatar Aang was a male Air Nomad born in 12 BSC and the Avatar during the century-long conflict known as the Hundred Year War. His immediate predecessor was Avatar Roku, and his immediate successor is Avatar Korra. During his lifetime, Aang, like all Avatars, was the only person capable of using all four bending disciplines: airbending, waterbending, earthbending, and firebending. He was also one of a select few Avatars, and one of the first in many cycles to learn the ancient art of energybending. Aang was the first Avatar seen using the technique, and Avatar Korra was the second known Avatar to utilize energybending.
Shortly before the beginning of the Hundred Year War, Aang was frozen in an iceberg for a hundred years. He 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. It fell to Aang, the last airbender and the Avatar, to put a stop to the War by mastering the other three elements and defeating the Fire Lord, Ozai. He remained something of a goofy, kind kid at heart throughout this year-long struggle, despite the overwhelming loss of his people and the heavy burdens he had been forced to bear. After his victory over the Phoenix King, Aang began a romantic relationship with his close friend, Katara. The couple eventually married and raised a family, which includes three children: Kya (a waterbender), Bumi (a non-bender), and the youngest, Tenzin (an airbender).
By the time of the Air Nomad Genocide, Aang was already an airbending master, the youngest in history. Aang achieved his mastery tattoos when he mastered thirty-five of the thirty-six tiers of airbending and invented a new airbending technique, the "air scooter". The element of air was the one he utilized the most in battle. Once Aang began to learn the other elements, for tactical purposes he relied less on airbending, though it continued to remain his signature element. As a master, Aang's skill with airbending was exceptional, being able to fight on-par with strong and powerful masters or against large numbers of opponents, despite not finishing his airbending training. He had been shown to create tornadoes and currents of air strong enough to lift or deflect extremely heavy objects. Aang's skill with air was great, even perilous, though his pacifistic Air Nomad nature halted the use of air as a deadly weapon, unless he was enraged or in the Avatar State. Instead, Aang used airbending for pure defense, evasion or other round-about methods of combat other than aggression. When not in battle, Aang used airbending in his everyday life, often for flying with his glider, or simply to augment his natural agility. While in the Avatar State, Aang's airbending power was magnified to the point he could erode solid rock away with a powerful gust of air.
Aang's airbending skills, especially his skill with the "air scooter" greatly improved over time, evolving from being able to ride one to creating multiple air scooters simultaneously without any difficulty. At age forty, Aang was shown to have mastered the air scooter to a much greater degree. This version was superior in terms of size and duration when compared to the ones he showed as a child and was capable of being used as a high-speed method of transportation, as Aang quickly caught up with Yakone, despite the latter having a good head-start. Aang was also capable of standing on the scooter, instead of sitting on it as he had done before.
Aside from his individual skill, Aang was also shown as a capable teacher, as he passed on the full extent of his airbending knowledge and techniques to his son Tenzin, who became a powerful master airbender in his own right
Although Aang was originally better at waterbending than his fourteen-year-old friend Katara, his lack of focus allowed Katara to surpass him as she was later deemed a waterbending master after rapidly developing her skills while training under Master Pakku. Katara became Aang's teacher when they took their leave of the North Pole. Aang first showed prodigious skill in waterbending, being able to easily create a huge wave on his first try. Aang had great skill with waterbending, though it was one of his least used elements in battle, instead favoring other readily-available elements such as earth or air. He did not carry a water skin, preferring to bend from large sources of water such as rivers, lakes, or oceans. His control over the element was monumental, capable of creating massive tidal waves, albeit with the help of the Moon Spirit, or bending entire streams of water. He was even able to extinguish a powerful, comet-enhanced blast of fire from Ozai, then used the water to briefly put the Fire Lord on the defensive. While in the Avatar State, Aang could bend an entire ocean to rise, mimicking the moon pulling the tides, to cover an entire forest. He was also capable of compressing massive volumes of water into smaller streams, (a normally incomprehensible skill) allowing an increase in force and pressure and making it easier to transport.
Because earthbending contrasted Aang's personality and his native element, air, he had great difficulty learning the bending art. Airbenders relied on indirect methods of combat, while earthbending required a head-on approach. When Aang was forced to protect Sokka from a saber-tooth moose lion he stood his ground rather than avoiding conflict, showing an earthbender's attitude; he was able to earthbend soon thereafter. His earthbending improved greatly, allowing him to utilize air, water and earthbending in combat together effectively. Earthbending had even become Aang's second most used fighting style behind airbending, due to its general availability. Aang was capable of bending large boulders, sending massive columns of rock flying, or forming earthen armor around his body for protection. While in the Avatar State, Aang could manipulate massive columns of rock, compress boulders into pebbles, or send rocks flying at high speeds in rapid succession, while requiring no physical connection with the ground to earthbend. It is unknown if Aang ever learned to bend metal, despite expressing interest in doing so only sarcastically while sabotaging the drill at Ba Sing Se before the technique was developed by Toph. Aang eventually learned to fight and bend blindfolded, detecting things by using Toph's seismic sense.
Despite the proficiency with which Aang used earthbending in his fight with Ozai, Toph had expressed an opinion that he could still improve; however, it was unclear if she felt he had not yet mastered it or if he could simply improve more.
While normally the Avatar must learn the four elements in the proper cycle, Aang was given the opportunity to learn firebending early from Master Jeong Jeong, instead of first mastering water and earth, in addition to his mastery of air. While training, Aang's impatience to learn the basics of firebending resulted in him harming Katara, an accident which caused him great shame. He swore from then on never to firebend again, out of fear of losing control again. It was not until after the invasion plan failed that Aang sought to learn firebending again. After accepting Prince Zuko as his teacher and discovering the true meaning of firebending from the dragons Ran and Shaw, Aang no longer feared firebending and began his training in the bending art. He was shown to be quite skilled, yet initially reluctant to show the aggressive attitude required for firebending. Aang was capable of performing the ancient Dancing Dragon form, the breath of fire while simultaneously firing a stream from both hands, and produce highly strong and powerful kicks and blasts able to incapacitate a Fire Nation airship with the help of Sozin's Comet which had greatly strengthened and enhanced his firebending abilities to numerous power levels at the time. In preparation for his face off with Fire Lord Ozai, Zuko taught Aang lightning redirection, a highly advanced and unique technique of firebending that Zuko's paternal uncle Iroh invented by observing waterbenders. While in the Avatar State, Aang could create exceedingly strong and highly destructive streams of fire, as well as melt solid stone
After being endowed with the knowledge from a lion turtle, Aang was able to use an ancient form of bending that precedes all other bending called energybending, which he used to strip Ozai of his natural firebending abilities, leaving the Fire Lord permanently drained and in a state of weakness. According to the lion turtle, before the Avatar existed, people did not bend the four elements, but the life force energy within themselves. However, in order to bend another person's life force energy, the energybender's own life energy must be unbendable, or they could become corrupted or even destroyed. It had been confirmed that Aang was not the first Avatar to learn energybending; however, there were very few who have learned this particular bending art and even fewer who have used it due to its dangers. While the full range and potential of energybending is unknown, it is known that it allows the bender to both strip and restore a person's bending abilities and transfer knowledge from one person to another.
At age forty, Aang's energybending skills had progressed, as he was able to strip Yakone's bending abilities almost immediately with minimal effort, unlike when he stripped Ozai's bending. He also demonstrated the ability to restore a person's bending, as seen when his spirit appeared before Korra and restored her abilities that had been taken by Amon's bloodbending. At the same time, Aang imparted the knowledge of energybending and control of the Avatar State onto Korra.