Legend of Korra transformed the world that was established in Avatar: The Last Airbender, and vastly improved the bending styles from the original show. Taking place 70 years after the events of the original series, Legend of Korra is set in the new Republic City, a modern and urban center of the Earth Kingdom that was established by Avatar Aang. Not just the setting has changed, as Legend of Korra also introduces new ways for the benders to use their power that goes above and beyond the original show.
Avatar: The Last Airbender hinted at the possibilities with bending in the original show. Toph Beifong invented a new subtype of earthbending called metalbending, which was previously thought to be impossible. Toph also used earthbending as a way to see her surroundings, and was able to sense if someone was lying. However, Avatar: The Last Airbender rarely showed its benders doing anything past basic elemental bending, focusing mostly on the journey of Aang and his friends as they try to defeat Fire Lord Ozai.
Legend of Korra immediately improved on the bending in Avatar: The Last Airbender by introducing pro-bending in the first episode, a competitive sport in Republic City where two teams of benders battle each other in an arena. After introducing the sport, Legend of Korra continued to improve the bending styles throughout the show in increasingly innovative ways. The show does this by taking advantage of its more modern setting to blend technology and bending in creative ways. Here are some of the improvements that Legend of Korra made to the bending from Avatar: The Last Airbender.
In Legend of Korra season 3, the show introduces Ming-Hua, a congenitally armless waterbender who assists Zaheer in kidnapping Avatar Korra. Ming-Hua is a powerful waterbender who uses her bending skill to create tentacle-like prostheses for her arms, using them skillfully as a weapon throughout the show. Ming-Hua is one of Legend of Korra's more formidable villains, and her skillful use of the protheses is partly what makes her so deadly. Ultimately, her water-tentacles also lead to Ming-Hua's downfall, when Mako directs lighting into them and kills her.
Legend of Korra also expands on the waterbenders ability to bloodbend with its season 1 villain, the Equalist leader Amon. Amon is a waterbender that manipulates bloodbending to take away people's ability to bend, using the rare bending technique in a new way from Avatar: The Last Airbender. Among is a horrifying villain, and his ability to take away people's bending using his waterbending is a terrifying improvement on the bending style.
Zaheer, the primary villain in Legend of Korra season 3, becomes an airbender following the Harmonic Convergence. A naturally skilled bender, Zaheer gains the rare ability to fly following the death of his girlfriend, P'li, when he lets go of his earthly ties and achieves total freedom. Only one other airbender in existence, Guru Laghima, was able to master flying - until Zaheer learned from his teachings 4,000 years after Laghima's death to help capture the Avatar. The airbending technique was never introduced in Avatar: The Last Airbender, since the airbenders were wiped out, but the reintroduction of new airbenders in Legend of Korra hints at more powerful abilities that are still undiscovered.
The other major airbending innovations comes from Tenzin's daughter, Jinora. Jinora discovers that she is sensitive to the spirit world, and develops the ability to separate her spirit self from her body using spiritual projection. She uses spiritual projection to travel to other parts of the world unnoticed, and send messages across long distances. While the spirit world and some spirit abilities existed in Avatar: The Last Airbender, the spirit world is more important in Legend of Korra due to Korra's decision to permanently leave the portals to the spirit world.
Legend of Korra introduces a more urban and modern world than the one in Avatar: The Last Airbender, and includes the invention of the biplane. Along with other inventions built by Asami Sato's Future Industries, the biplane can operate without any bending at all - but Korra and Mako power a damaged plane using their combined firebending in Legend of Korra season 2. Harness the ancient bending style and combining it with modern technology allows the broken plane to fly without its engines, and allows team Avatar to defend Republic City from an attack. The ability to power the plane using bending is a great example of how Legend of Korra blended the supernatural and the mundane, and one of the ways that it improves bending throughout the show.
Although metalbending was invented by Toph Beifong in Avatar: The Last Airbender, the bending technique is much more common in Legend of Korra. This is partially because Toph's daughter Suyin opened a metalbending school to train other earthbenders and popularize the practice. Due to the widespread knowledge of metalbending, the style is now used in a variety of inventive applications such as the Republic City Police controlling their rappelling cables, or assembling armor - but the biggest departure from traditional metalbending was with acupuncture.
In Legend of Korra season 3, Lin Beifong visits Guo, who uses his metalbending to administer acupuncture and help his patients unblock their chi. The practice brings up memories that Lin had repressed, reliving how she got her scars and the painful circumstances that led to her strained relationship with her sister. Combining the traditionally solid and grounded earthbending style with chi-blocking significantly improves the bending style in Legend of Korra.
Legend of Korra greatly improves the bending styles introduced in Avatar: The Last Airbender by introducing new subtypes of bending and using the techniques in increasingly innovative ways. The more widespread use of metalbending means that it is used more inventively, and the introduction of modern technology allows for creative interactions with bending. Despite that, Legend of Korra always returns to its more spiritual roots by using bending to manipulate chi. Although the world introduced in Avatar: The Last Airbender brought us the basics of the bending styles, Legend of Korra vastly improves the application of bending during its four short seasons.