Prince Zuko's scar is one of the most memorable elements of Avatar: The Last Airbender, and in the season 2 finale Katara offered some hope that it could be healed. Healing is a subset of waterbending, and Katara quickly grows to become one of the best healers in the world. Considering her incredible skill as a waterbending healer and the fact that Zuko joins Team Avatar in season 3, fans have wondered why she didn't heal his scar during the series or after its conclusion.
Avatar reveals the origin of Zuko's scar in season 1, episode 12, "The Storm." The scar is the result of an Agni Kai firebending duel with his father, Fire Lord Ozai, who ordered the Agni Kai after Zuko opposed a Fire Nation general's plan to bait skilled Earth Kingdom fighters with inexperienced Fire Nation soldiers. When Zuko refused to fight his father, Ozai burned half of his face and banished him from the Fire Nation. Ozai always treated Zuko cruelly, and this fight marks the beginning of Zuko's long journey to redemption.
Even though the scar is such a strong reminder of Zuko's past trauma, he never asks Katara about her offer to heal it, and she never makes the offer a second time. There are a number of reasons Katara may not have healed Zuko's scar, including the fact that she may not have been able to and the very real possibility that Zuko wanted to keep his scar.
Katara Offered To Try And Heal Zuko's Scar
Despite being enemies for so long, Zuko and Katara grow closer in season 2, episode 20, "The Crossroads of Destiny." While the two of them are imprisoned in the Crystal Catacombs under the Earth King's palace, Katara confides in Zuko about the Fire Nation killing her mother, and he apologizes and tells her about his own mother, allowing them to connect for the first time in the series. Beginning to see Zuko's change of heart, Katara offers to heal his scar with waterbending.
In the finale of the first season, Master Pakku had gifted Katara with a vial of spirit water from the Spirit Oasis in the North Pole. The water's spiritual energy grants it powerful healing properties. Katara had saved the spirit water for something important, and when she senses Zuko's regret in the Catacombs, she thinks that the spirit water can heal him. However, Aang and Iroh rescue them before she can begin the healing process.
Of course, everything changes when Zuko sides with Azula, taking several steps backward on his journey to redemption. In the same episode, Azula strikes Aang with a fatal bolt of lightning, and Katara revives him with her spirit water. She uses her entire supply of spirit water to treat Aang, and, when Zuko joins Team Avatar in season 3, she does not offer to heal his scar again.
Zuko Still Has His Scar In The Legend of Korra
Zuko is one of the main Avatar characters to return in The Legend of Korra. He appears throughout season 3 and helps in Korra's fight against the Red Lotus. His scar is still visible, proving both its severity and the fact that it hasn't been healed in the 70 years since the conclusion of Avatar: The Last Airbender. Not only was Katara a master waterbender, her daughter Kya also proved to be especially adept at using waterbending to heal people - including their spiritual wounds. With the war over, Katara could also have taken Zuko back to the Spirit Oasis to attempt the healing process with the spirit water there. Zuko still being starred in Zuko raises two possibilities: either he tried to have his scar healed and it failed, or he wanted to keep the scar.
Katara May Not Have Been Able To Heal Zuko's Scar
Even when Katara offers to heal Zuko's scar with the spirit water in season 2, she is unsure that it will help. She's never used the spirit water to heal before, and there's a chance that it would not heal a years-old scar like Zuko's. Despite Katara's prowess as a waterbender, it's possible that Zuko's scar is beyond both her power and that of the spirit water.
Aang's own recovery process provides evidence that Katara may not have been able to heal Zuko's scar with spirit water. Katara uses the spirit water on Aang for months on Aang's injury, and he still ends up with a large scar from Azula's lightning strike. His scar is fairly recent compared to Zuko's, which he has had for 3 years. Since even the spirit water couldn't heal Aang's physical scarring, it's possible it wouldn't have healed Zuko's scar even if Katara had tried.
Why Zuko May Have Wanted To Keep His Scar
Despite the traumatic memories associated with his scar, Zuko never seems particularly ashamed of it. Throughout season 1, his hairstyle ensures that it's completely exposed, showing his identity to the world. In the second season, Zuko tells Katara that he's beginning to accept that he won't be rid of the scar, telling her, "I used to think this scar marked me - the mark of the banished prince, cursed to chase the Avatar forever. But lately, I've realized I'm free to determine my own destiny, even if I'll never be free of my mark."
As much as it caused him pain, Zuko's scar and the day when he received it are key parts of who he is and his destiny going forward. If he hadn't been scarred and banished, he would not have understood the horrors the Fire Nation inflicted on the world and ultimately switched sides to Team Avatar. He wouldn't have come to recognize Iroh as his main father figure, or been able to overcome Ozai. The scar is a reminder of Zuko's pain, but it is also a reminder of his path to becoming a good person and a wiser, more noble Fire Lord than his father was.
Zuko's redemption arc is so brilliant in large part due to his acknowledgment of his past traumas and his subsequent growth. His scar is a physical reminder of his hurt, and by keeping it and embracing it, it's clear that he has grown as a character. Getting Katara to heal his scar would have been an attempt to erase his past, and would have bought into a tired narrative of physical healing being the same as emotional healing. Avatar: The Last Airbender is too smart a show to fall into that trap.