The Fire Lord of the Fire Nation. He is also Avatar Aang's Firebending Master and advisor.
When Zuko was eleven years old, his cousin, Lu Ten, was killed in battle. General Iroh, devastated by the loss of his only child, abandoned his 600 day siege of the Earth Kingdom capital city, Ba Sing Se. During an audience with Fire LordAzulon, Ozai showed off Azula's prodigious firebending skill and knowledge of military strategy, both outstripping Zuko's. Azulon was unimpressed by these exercises and demanded Ursa and her children leave and Ozai be frank about his reasons for wanting the audience. Azula and Zuko eavesdropped on their conversation as Ozai voiced his desire to be made heir in Iroh's place, justifying this course of action by pointing out that Iroh's overwhelming grief and subsequent erratic behavior made the date of his return from war uncertain and he had no remaining heirs to carry on his line. Azulon, however, was outraged and declared angrily that Iroh had suffered enough, but Ozai's suffering had just begun.Frightened, Zuko ran away while Azula stayed to watch. Later, he was in his room trying to sleep when Azula came in and mockingly told him that Azulon's punishment for Ozai is that Ozai must kill Zuko, as he wanted him to know what it felt like to lose a first-born child. Ursa, hearing the commotion, came in and took Azula away, declaring it was time that they talked. Zuko, left behind, chanted quietly to himself, "Azula always lies." Later, he was awakened again, but this time by his mother. She told her sleepy son that everything she had done, she had done to protect him, and instructed him not to forget who he was no matter how much things may change. The next morning, he immediately remembered what transpired the night before and ran frantically through the halls searching for his mother. He found Azula, who blithely told him Azulon died the previous night and their mother was missing. As she played with his pearl dagger (a gift from his Uncle Iroh), she mocked him and noted their mother was not there to make her give it back. Eventually, he found Ozai in the gardens of the palace and demanded to know where his mother was. Ozai did not answer and he hung his head in sorrow. At Azulon's funeral, the Fire Sage conducting the ceremony named Ozai the new Fire Lord upon Azulon dying request.
Zuko wandered through the Earth Kingdom, passing through forbidding and uninhabited areas. Despite his worsening hunger and lack of supplies, he decided not to rob a young couple when he noticed that the woman was pregnant. Eventually, he stumbled upon a small town that was regularly harassed by a troop of unscrupulous Earth Kingdom soldiers. Zuko stood up to those soldiers, impressing a young boy named Lee, who invited Zuko back to his family's farm for food and shelter. He spent the day helping with chores, and thinking of his own, far less happy childhood. Zuko acted as something of a substitute brother for Lee, whose older brother was off fighting in the war, even giving Lee a quick lesson in how to use dual broadswords when Lee's curiosity prompted him to take them. As Zuko was preparing to leave, the Earth Kingdom soldiers rode to the house and gave the news that Lee's older brother's battalion had been captured.Lee's father decided to join the army to try to get his son back. Lee asked Zuko to stay and take care of them, but Zuko declined. Before leaving, Zuko gave Lee the dagger that he received from Iroh as a boy.
After Zuko left town, Lee's mother came to him, telling him how the soldiers had come back after her husband left to harass the family and took Lee away when he threatened them with the dagger. Having no one else to turn to, she asked Zuko to save him. Zuko denounced the soldiers as common bullies and defeated most of them easily, but the ringleader was an earthbender and Zuko was unable to beat him using only his broadswords. After recalling his mother's last words to him before her disappearance, to "never forget who you are", Zuko firebent to save himself and announced his identity proudly to the town. He retrieved his dagger from the beaten ringleader and tried to give the knife to Lee, but Lee declined and claimed his hatred for Zuko due to his former alliance with the Fire Nation. Despite what he had done for them, the townspeople rejected Zuko because of his identity and he departed, alone, with his dagger.
Zuko followed the progression of a tank train belonging to Azula, who was in turn relentlessly hunting and harrying Aang and company. He eventually came across Azula in a deserted town where she and Aang were about to face off. He assumed a fighting stance and warned his sister to leave Aang's capture to him. Not willing to budge, she prepared to battle herself. The three stood off, waiting for one to make the first attack. Eventually, Azula fired at Zuko, knocking him over. When she proceeded to attack Aang, a three-way battle ensued.
Azula dominated the fight by launching many powerful attacks and keeping Aang and Zuko on the defensive. Zuko traded several fire attacks with her, and pursued her into a building, where she finally landed a knock-out blow to Zuko. After several minutes, Iroh, who had been following Zuko and watching over his nephew from afar, shook Zuko out of unconsciousness. The two of them joined Aang and his friends, who had joined him earlier. All six cornered Azula, who feigned surrender, only to attack and badly wound Iroh in a moment of distraction. Zuko, Aang, Katara, and Toph each launched an elemental attack, but Azula disappeared, utilizing a clever firebending move. Zuko ran to his wounded uncle, grief-stricken. When Aang and his companions approached, he angrily demanded that they leave. Katara offered help, but Zuko launched a fire blast at them. They ran away, leaving Zuko to tend to his uncle's injuries.
While growing up in the Fire Nation, Zuko showed no extraordinary skill in firebending. In his teen years, however, his ability began to develop significantly under his Uncle Iroh's tutelage, most noticeably during the last year of the Hundred Year War. He became able to fight on par with much more experienced firebenders, showing himself to be a late bloomer. Having continuously refined his skills, he has reached the point of becoming a firebending master, but despite his skill and fast development as a firebender, he has noted on more than one occasion that he is not as skilled or as powerful as his younger sister, Azula.
As a child, Zuko could only create small bursts of flame and was by no means focused or controlled in his bending, but by the time he was thirteen, he was confident enough in his abilities to readily accept a challenge of Agni Kai against General Bujing.
Around the time of Aang's discovery at the South Pole, Zuko was still learning the basics from Iroh yet was skilled enough to momentarily knock Aang off his ship, but he was defeated when Aang went into the Avatar State. He utilized what he had been taught to defeat Zhao, an older and more experienced master firebender. Throughout his pursuit of Aang, he demonstrated his skill often; he defeated multiple foes on two occasions. Later, his skill grew. He fared well in a duel against Aang, delivering multiple fire blasts for a sustained period without tiring, but was defeated when he was paralyzed by June's confused shirshu. He created a shield of fire to protect himself from a massive explosion on his ship. During the Siege of the North, he fought Katara while the moon was nearly full. He held his own against her while she was strengthened by the moon, but needed the power of the sun to gain the upper hand and defeat her with one fire blast. He also landed a decisive victory in a rematch against Zhao.
After the Siege of the North, Zuko's firebending became more advanced and powerful. At first, he was unable to land any blows against Azula, and was defeated rather easily. He fought somewhat better during the Confrontation at Tu Zin; in a three-way battle with Azula and Aang, he traded several fire blasts with his sister and kept the Avatar on the defensive. As his travels in the Earth Kingdom continued, however, he learned more advanced firebending techniques from Iroh, such as lightning redirection, becoming more efficient and refined. During a battle with the Rough Rhinos, he sent a small bolt of fire through Vachir's bow, breaking the string. He demonstrated the ability to fire multiple small blasts through two fingers, rather than his whole fist. During the battle in the Crystal Catacombs, he demonstrated how far his prowess had grown. His fire blasts were more powerful, and he charged his attacks before releasing them, creating enormous blasts of fire. He also demonstrated the ability to create two fire-whips. He battled evenly with Aang, even though he had skillfully used airbending and earthbending. After switching opponents with Azula, he battled evenly with Katara, a waterbending master who had the upper hand against Azula.
Little was seen of Zuko's firebending after he returned to the Fire Nation; however, he was confident enough in his abilities that he offered to teach Aang. He utilized a wall of flame to stop an attack from Combustion Man, and was capable of dodging many of Toph's rocks which she hurled at him, though her earthbending was impeded due to Zuko accidentally burning her feet. Later, he temporarily lost his firebending from a corresponding lack of rage, the former source of his power. In order to reconnect with the original source of firebending, he and Aang traveled to the ancient city of the Sun Warriors together. There, Zuko learned "TheDancing Dragon", an ancient firebending form that he performed alongside Aang. Learning this form appeared to have influenced his style of firebending to be more fluid, creating a more dancelike form as opposed to the rigid, militaristic forms commonly used by Fire Nation soldiers. He was also challenged by the Tribesmen to carry a piece of the Eternal Flame all the way up to the cave of the masters. Zuko and Aang performed their newly learned technique in unison with the dragons, who engulfed them in a spiral of multi-colored flames. After viewing this, Zuko found a new source of power in reverence for fire's power as a source of life and energy: "the sun inside you". His stylistic differences and skill are demonstrated at the Boiling Rock where he briefly battled against Azula alongside Sokka. During the fight, he deflected many of Azula's fire blasts with only his arms or his own fire, and traded fire balls with her. He later faced Azula again and dueled her evenly for several minutes. He fired several large and powerful fire blasts, deflecting many of her attacks. Later, he attacked Aang with powerful fire blasts to make him fight back. When he chased him into Ozai's old family vacation home, Zuko created several lashes of fire to envelop his surroundings and augmented them to the shape of the hallway Aang was running through.Furthermore, he used his firebending in conjunction with his broadswords, demonstrated use of fire daggers, and limited use of breath of fire.
During his training with Iroh, Zuko attempted to learn how to create lightning. His inner turmoil, however, rendered him unable to achieve the required peace of mind, and his attempts to produce lightning would only explode in his face. Instead, Iroh taught him how to absorb and redirect lightning. He later employed this technique against his fatherand Azula to protect Katara. In the latter engagement, Zuko redirected the blast in an improper stance, as he had jumped into the lightning's path, and so failed to redirect it completely and resulted in serious injury. Though he seems to have overcome his inner turmoil, he does not create lightning for the remainder of the series.
With the power of Sozin's Comet, Zuko's firebending was tremendously enhanced. He fought Azula one final time in an Agni Kai, unleashing extremely powerful sheets of flame. This time he held the upper hand, not showing any visible strain in exchanging and blocking Azula's attacks while she was pushed toward exhaustion and increasing mental instability. He displayed several incredibly powerful techniques: blocking an enormous stream of fire with a short fire-blast, spreading to take the shape of a wall and split the stream, unleashing an enormous charged-blast, which Azula was unable to block, forcing her to dodge, propelling himself into the air, charging his fire and sending down a fire attack as he came. His final attack was a fire tornado he created with his feet while spinning, knocking Azula off her feet.
After the War and assuming the mantle of Fire Lord, Zuko's firebending remained as sharp as before and under strict control, despite the mental and emotional turmoils he was struggling with due to his new position. He evaded several attempts on his life, particularly the attempt of Kori Morishita, an earthbender and skilled weapons user, whom he disabled in a matter of minutes. During the battle for Yu Dao, Zuko's skills were again on display as he managed to single-handedly overwhelm a large number of Earth Kingdom soldiers with minimal effort and stand on equal footing against General How. The flames he produced were also hot enough to instantly melt metal chains.
He handled Azula quite well during their fire fights throughout the search for their mother, blocking her fire blasts and defending his friends simultaneously, especially during her psychotic episodes. This demonstrates how far he has come, being able to match Azula in certain terms of raw power, despite not being able to generate lightning or blue fire.
During an ambush by the New Ozai Society, Zuko also demonstrated the ability to generate a fire vortex featuring green and purple flames, marking the first instance that a human has created dragon fire.
At the age of 88, Zuko still proved to be a capable fighter, although less agile.
Firebending is an ability based off of the martial art of Shaolin Kung Fu, and allows for the manipulation and generation of the element of fire, lightning, and heat. The fight style for this art is can be aggressive and forceful. Emotions can affect the intensity of firebending, and celestial events such as Sozins Comet can greatly enhance firebending. At an early age Zuko was trained in firebending, and although he wasn't quite as prodigious as his little sister Azula, he trained hard and eventually gained mastery over the element. He has many feats which highlight his mastery over this ability.
Zuko learned the true meaning of firebending from it's original masters, the dragons, and learned the Dancing Dragon firebending form.
He defeated Commander Zhao in a fire duel, and it is implied that Zhao is a master firebender
He is easily able to deflect fiery attacks
Made a fire shield capable of defending him against Combustion Man's explosion
Zuko is an elite fighter. He was trained in the Fire Nation how to use dual swords. He also shows skill in hand to hand combat.
He stalemated Jet in a sword duel
He has no problem disarming enemies while being swarmed, and without use of his sword
His combat skill is enough to frighten away earthbending soldiers
He is capable of channeling his firebending through his sword
Stealth, Deception, and Resourcefulness
Zuko has proven himself to be a very stealthy and resourceful. He occasionally dons a secret identity known as the Blue Spirit, a nonbender criminal who relies on stealth and deception to achieve personal goals
He is undetected while sneaking into a heavily guarded Fire Nation compound
He in laying traps and using items to lure and pick off guards, as well as slice through metal chains with swords.
Another display of his deception and resourcefulness against a Dai Li agent
He doesn't need to be in persona to use these skills, as he uses them against Yon Rha with Katara
Zuko has shown very impressive displays of strength, durability, acrobatics, and reaction speeds.
Durability: His most impressive feat is tanking an explosion that destroyed his ship, and keep in mind that explosion was an assassination attempt on his life. Zuko has also easily walked off point blank explosions and again with Azula. He also has taken powerful earthen attacks.
Zuko is also able to swim in the arctic here at 15:10 and superheat through ice