The animated world of Avatar: The Last Airbender and The Legend of Korra features the awesome power of the Avatar state as the ultimate expression of elemental bending and spiritual power. Avatar Aang and Avatar Korra were often seen going into the Avatar State either by instinct or on purpose, and the power of the Avatar State could usually save the day. Interestingly, however, the Avatar State was often as terrifying as it was heroic.
Each Avatar, from Wan to Korra, bore an immense responsibility to use the Avatar State wisely and not abuse it, and most of all, the Avatar is most vunerable while using the Avatar State’s powers. It is often scary when Aang or Korra use the power of the Avatar State, since each of them almost ended the Avatar Cycle by accident while in that mode. In other cases, Aang and Korra were scary because of what they did to everyone else in the Avatar State, or because the Avatar State represented their emotional distress.
10
Aang Froze Himself in the Avatar State to Avoid Drowning
Book One, Episode 12: “The Storm”

Chronologically, the first time Aang went into the Avatar State happened 100 years before he met Sokka and Katara. Avatar fans saw it happen in a flashback sequence, where Aang told Katara about the night he fled the Southern Air Temple in distress. Aang already felt overwhelmed as the new Avatar, and he felt even worse when a nasty ocean storm caused him and Appa to nearly drown.
In that moment of crisis, Aang went into the Avatar State out of sheer instinct, which included his first instance of waterbending to freeze himself and Appa. It was scary to see Aang have such a close brush with death like that, and worse yet, it meant the world had no Avatar to help when Fire Lord Sozin launched his historic war to take over the entire world.
9
Aang Summoned Roku’s Power in the Avatar State
Book One, Episode 8: “Winter Solstice, Part 2: Avatar Roku”

Not only can the Avatars give each other wisdom and insight with words, but they can even grant each other their powers if need be. Aang took advantage of that feature of the Avatar State when Admiral Zhao’s team had the Gaang cornered on an island in the Fire Nation, with Aang allowing Roku to take over his body in a moment of peril.

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It was equally thrilling and terrifying to watch Avatar Roku wield overwhelming lavabending to destroy the entire island and force the villains to flee. That showed what a dreadfully destructive price the heroes sometimes had to pay just to survive the war, highlighting the grim reality of the Hundred-Year War raging around them.
8
Aang Went Into the Avatar State When He Saw Gyatso’s Remains
Book One, Episode 3: “The Southern Air Temple”

Aang’s first major usage of the Avatar State on-screen happened in a moment of intense personal turmoil. Aang didn’t even mean to go into the Avatar State and cause devastation with his airbending, but he did just that upon seeing monk Gyatso’s remains. This moment established the Avatar State as an uncontrollable force at the mercy of Aang’s emotions, which created some tension.
Fortunately, Aang had Katara there to coax him back out of the Avatar State, though they and Sokka were still shaken by what had happened. And even after Aang ended the Avatar State, he was still in anguish, coming to terms with the reality the Air Nomads were gone aside from him. To his credit, though, Aang found a way to handle his grief and resumed the journey in good spirits, including the addition of Momo the flying lemur.
7
Aang Fused With the Ocean Spirit Via the Avatar State
Book One, Episode 20: “The Siege of the North, Part 2”
Aang entered the exotic Spirit World to find aid for the Northern Water Tribe, but he was too late, and Admiral Zhao unwisely killed the Moon Spirit. With waterbending gone and the Northern Water Tribe on the brink of destruction, Aang entered the Avatar State to change the tide of battle, literally and otherwise. By fusing with the surviving Ocean Spirit, Aang became a watery kaiju unlike anythng Zhao had ever seen.
Once again, the Avatar State was both heroic and terrifying as Aang swept aside the Fire Nation fleet with his titanic powers. Countless Fire Nation ships were destroyed or driven back, and by the time Aang was done, he was worn out. He wearily stood on the Water Tribe’s wall, barely able to stand after wielding such immense power in a moment of crisis. That moment, among others, helped inspire Aang to find a way to properly control the Avatar State in future adventures.
6
Aang Went Berserk in the Avatar State With General Fong
Book Two, Episode 1: “The Avatar State”

Early in Book Two, Aang hoped to harness the Avatar State as a tool to be carefully controlled, but he had no such luck. Due to his limited training, Aang wasn’t sure how to enter the Avatar State at will or control himself while he was in that state. General Fong was eager to help with that training, but the results did more harm than good.

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Fong tricked Aang into thinking he had crushed Katara to death in the earth, prompting Aang to enter the Avatar State and wreak havoc on Fong’s men. Ultimately, Aang failed in his training, and everyone was more afraid of and wary of the Avatar State than ever. Aang would need not General Fong, but Guru Pathik to show him how to control the Avatar State via his freed chakras.
5
Aang Tapped Into the Avatar State Upon Hearing of Appa’s Fate
Book Two, Episode 11: “The Desert”

Another instance of Aang entering the Avatar State due to emotional distress arrived in the Siwong Desert, where Aang met some sandbenders who had kidnapped Appa. Being highly protective of Appa and relying on the sky bison for transport, Aang couldn’t help entering the Avatar State in a moment of rage.
Aang could have hurt or even killed the sandbenders as he threw around powerful, sandy winds, but Katara wouldn’t let that happen. Once again, Katara was Aang’s emotional lifeline, unwilling to let Aang lose himself to rage, grief, and power. That helped reinforce the power of friendship Aang had with his team, because he needed more than bending power to save the day and become a great Avatar.
4
Aang Almost Died in the Avatar State Under Ba Sing Se
Book Two, Episode 20: “The Crossroads of Destiny”

Normally, the Avatar State’s power is meant to help the Avatar win a fight and discourage any more violence or chaos, but the opposite happened when Aang willingly entered the Avatar State underneath Ba Sing Se. He opened his chakras and floated into the air to win the fight, only for Princess Azula to zap him and almost kill him.
That was a scarily close brush with death, proving Roku right that the Avatar is oddly vulnerable while in that state. Worse yet, even after he was healed and saved by Katara, Aang found himself unable to re-enter the Avatar State for some time, robbing him of his best weapon. In many ways, Azula broke Aang in that historic moment, but Aang would get his power back when he needed it the most.
3
Aang Needed the Avatar State to Defeat Fire Lord Ozai
Book Three, Episode 21: “Sozin’s Comet, Part 4: Avatar Aang”
Aang tried fighting Ozai with regular elemental bending, but with Sozin’s Comet fueling Fire Lord Ozai’s firebending, it was no good. Once again, Aang came scarily close to dying and taking the Avatar State with him, only for Aang to re-enter the Avatar State at the last possible second. Aang then went on a rampage, tossing the helpless Ozai around the battlefield with all four elements.

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Scariest of all was when Aang almost killed Ozai with a quad-elemental strike from high above, which nearly compromised Aang’s pacifistic principles. Aang refused to end it like that, much to Ozai’s contempt, but he had one more card to play: the art known as energybending. With it, Aang defeated Ozai without killing him, an inspirational example of someone getting the job done without compromising who they are.
2
Korra Entered the Avatar State Against Her Will When Zaheer Poisoned Her
Book Three, Episode 13: “Venom of the Red Lotus”

Avatar Korra used the Avatar State with care and finesse a few times, such as when she used it to amplify her waterbending to move aside a Northern Water Tribe fleet in her way. Only later did Korra’s usage of the Avatar State become something terrifying, with the Red Lotus poisoning Korra and forcing her into that state.
Korra knew if the Red Lotus killed her in that state, the Avatar Cycle would disappear, creating a moment of extreme peril. Korra had to fight both Zaheer and the poisonous mercury in her system, all while the Avatar State went haywire. It became a clumsy and unreliable weapon in Korra’s hands, and worst of all, Korra struggled to re-enter the Avatar State for some time after that.
1
Korra Couldn’t Defeat Kuvira Even With the Avatar State’s Power
Book Four, Episode 6: “The Battle of Zaofu”
Even after Korra physically recovered from Zaheer’s attack, she remained mentally unwell, which hampered her efforts while battling Kuvira just outsides Zaofu’s metal walls. In fact, Korra didn’t even try to enter the Avatar State until the last second, and when she did, it became clear Korra’s recovery had some ways to go.
It was scary and grim to see Korra barely enter the Avatar State, only for her mental trauma to take her back out of it as an Avatar who wasn’t ready for this. Not only did that cost Korra the duel, but it also gave her a serious mental obstacle, her trauma and fear that hit harder than any mercury. That was also a chillingly realistic barrier for Korra to overcome, since mental trauma and fear can hold anyone back from doing what they must.