The Avatar franchise, released on Nickelodeon, is nominally targeted at children. But the franchise has always been a bit more mature than other cartoons, approaching adult topics and examining the repercussions of its battles. This includes featuring some death scenes that are genuinely shocking in their brutality and suddenness.
Here are all the most intense deaths from the Avatar franchise, across both The Last Airbender and The Legend of Korra.
ZHAO
Zhao was a general in the Fire Nation army. A ruthless and ambitious strategist, he was one of the most consistent threats of the first season of Last Airbender. Like Zuko, he was committed to trying to catch the Avatar, but also quietly hated the young prince and actively tried to kill him more than once. He ultimately led the Fire Nation attack on the Northern Water Tribe during the climax of the first season, targeting the powerful spirits who resided there and empowered the moon and the ocean. Although Zhao killed the Moon Spirit Tui in an attempt to depower waterbenders, Yue was able to sacrifice herself to take its place and become the new Moon Spirit.
Zhao engaged in a duel with Zuko while trying to flee the Northern Water Tribe, but just as Zuko gained the upper hand, La the Water Spirit (who had briefly bonded with Aang while he was in the Avatar State) grabbed ahold of Zhao. Instead of taking Zuko's hand, Zhao is instead dragged under the water and presumably drowned. It's a brutal death, but it turns out only to be the beginning of his suffering. The Legend of Korra eventually revealed that Zhao's spirit was dragged into the Fog of Lost Souls. His spirit wandered through the mist, lost in madness and his worst memories. Notably, he attacks Aang's son Tenzin, believing him to be the Avatar. Tenzin leaves him behind, letting Zhao move further into the mist.
ROKU
Roku was the Avatar before Aang and a frequent spiritual guide for the young Avatar. A kindly but dedicated learner he became a powerful bender in his lifetime. He was also revealed to be best friends with Sozin, the prince of the Fire Nation. Sozin was even the best man at Roku's wedding. However, their friendship fractured after Sozin became the Fire Lord and his ambitions to bring "order" to the world forced Roku to step in and prevent his attempts to expand the Fire Nation. Roku and his friend battled, with Roku easily defeating Sozin. This dispute lasted for decades, with the pair refusing to speak to each other for years.
Recounting his demise to Aang in the third season of the series, Roku explains how a volcano near his home erupted, causing an explosion so massive that it could be seen from the Fire Nation capital. Roku was able to use the Avatar State to contain and stall the volcano for a time while his wife and the rest of the island's inhabitants fled.
Before he was consumed by the flames, Sozin arrived to lend his aid and the pair were able to use their bending to slow the lava flow. Roku saved Sozin by pushing him out of the way of a blast of toxic gas leaking from the volcano. Roku was effected himself, however, and was left blinded and choking. Roku begged his friend for help, but Sozin -- seeing a chance to end the Avatar's resistance of his ambitions -- left Roku to die. Joined by his dragon Fang, Roku was soon overtaken by the lava. It's a tragic death, with the betrayal from his best friend adding heartbreak to the demise.
NOATAK & TARRLOK
Tarrlok and Noatak were brothers, sons of the crime lord Yakone. Forced into exile by Aang, Yakone brutally trained them as they grew up. Noatak eventually ran away from home, leaving Tarrlok and his family behind. While Tarrlok eventually made his way to Republic City and by the events of Legend of Korra's first season had become a councilman for the Northern Water Tribe, Noatak rebranded himself as the mysterious terrorist Amon. Using his powerful bloodbending, Amon waged a war of intimidation against benders in the city by removing their abilities. He was eventually even briefly able to take away Korra's bending. One of his victims turned out to be Tarrlok, who was taken captive by Noatak.
When his identity was revealed to Republic City by Korra, he fled -- taking his brother with him. The pair escaped via speed-boat, leaving the city behind and reaching the middle of the ocean. They spoke about their former relationship, and Noatak revealed his hopes that they could find a way to find peace together. A defeated Tarrlok quietly had different plans, however. Tarrlok eventually put on a chi-blocker electro-glove and opened the gas valve of the speed-boat. Using the glove, he was able to set off an explosion that wiped out the pair of them in an instant, a sudden and shocking murder-suicide that closed the door on Yakone's family.
THE RED LOTUS
The Red Lotus was a terrorist organization introduced in the third season of Legend of Korra. A group of deadly bending prodigies, the four were revealed to have attempted to kidnap Korra in her youth. Their intention was to bring down the power structures of the world, setting up a more chaotic sense of "freedom" in their place. They failed in their attempt to take Korra, and were captured as a result. Imprisoned across the world, things changed after Harmonic Convergence awakened airbenders across the world, including Zaheer -- leader of the group. Breaking out of prison, he soon was able to free his compatriots: The snarky, lava-controlling earthbender Ghazan, the cruel, armless waterbender Ming-Hua, and the deadly, explosion-empowered firebender P'Li.
The four soon hunted down Korra, and were even able to capture her at the Northern Air Temple. However, Zaheer ended up losing his allies in quick (and violent) succession. Lin and Suyin dueled P'Li, leading Suyin to surround P'Li's head in a metal suit right as an explosion set off -- presumably decapitating her via her own explosion. When Korra's allies were able to follow after the Red Lotus and find Korra, Mako and Bolin entered into one-on-one duels against Ghazan and Ming-Ha. Mako was able to use his lightning bending to electrocute Ming-Hua to death during their battle.
Joining his brother against Ghazan, they were able to overwhelm the earthbender. Preferring death to imprisonment, Ghazan used his lava-bending to bring down the temple -- consuming himself with lava while Mako and Bolin escaped.