Avatar is an animated series created by Michael Dante DiMartino and Bryan Konietzko.
The Last Airbender: It centers around Aang, the incarnation of the spirit of the earth (known as the Avatar), and his quest to stop the tyrannical Fire Nation from taking out the other countries- the Water Tribes, Earth Kingdom, and Air Nomads. Aang's native nation, the Air Nomads, were already wiped out a century ago, hence the title.
In the Avatar universe some people are gifted with abilities to control an element depending on which ethnic group they're born in. The ability is inborn so if you're not gifted from birth you just received the short end of the stick. Those who get the power are referred to as "benders" of their element. You can only control one element. Earthbenders control rocks and minerals, and in one special case metals. Firebenders control fire and in more advanced stages, lightning, while waterbenders control water in all its physical states and bodily fluids, and can have low level healing powers. Lastly, airbenders control air and arguably farts. They control sneezes so it's only logical. Only the Avatar can learn to control all four.
The Avatar itself is reincarnated into a new nation every time he's killed i.e if he's killed as a Water Tribesman he is reborn as an Earth Kingdom citizen. The cycle goes Fire-> Air-> Water-> Earth ad infinitum. The only way to permanently kill the Avatar is to kill him/her as he reaches a super state dubbed the "Avatar" state. In that state he's pulling hurricanes and earthquakes so it's really really difficult. The show recently started a sequel series that takes place 70 years after the conclusion of the original called, Avatar: The Legend of Korra.
Powers of the Verse
Not too strong, but is not too weak. As a verse they are lacking in physical feats, although they can augment their striking strength and speed with their elements. They also possess elemental manipulation and are very versatile in their uses of it. In terms of destructive capacity they are for the most part they are in the large building+ range although they do have a particularly broken ability in bloodbending of their opponents, albeit this requires a full moon to pull this off .
The verse also possesses several powerful spirits including two spirits of the moon and ocean that can cause huge tidal waves, a killer panda spirit and a giant worm that eats your face for the lolz. When a celestial object known as Sozin's Coment passes every hundred years, firebenders gain a significant boost in power. It is believed that it grants firebender enough power to destroy a continent from a fleet of 20 airships within the course of a day, although they were foiled before they could pull this off, so this claim is somewhat dubious.
As far as Legend of Korra goes, after the introduction of Vaatu and Raava, who are possible lifewipers at full power, it has arguably passed The Last Airbender in terms of power. Kuvira also possessed a robot that could potentially destroy a city.
In addition, there are several chi blockers and Amon who can bloodbend and permanently block off people's bending skills. Metalbending has been further developed by Toph's daughter and her police force, using metal cables to restrain people and fly around the place like Spiderman. Bloodbending also no longer requires a full moon to perform. Very dangerous spirits. Earthbending got a new sub skill called lavabending that allows them to change earth into molten lava, which they can then control. Due to the nature of lava it's very powerful and destructive. The Equalists also got their hands on awesome war mechs.
Supporters and Opponents of the Verse
Not Jim Sterling
Koh the Face Stealer
Mother of Faces