* The Fire Lord Ozai: As the embodiment of firebending and the antagonist of the series, Ozai's power and ruthlessness are undeniable. Aang sees him as the ultimate threat to the world and his friends, which certainly creates fear. This is most evident in the final season, where Aang experiences nightmares and fears being unable to defeat Ozai.
* Azula: Azula is known for her cunning, manipulation, and powerful firebending. Her ruthlessness and unpredictable nature are shown to be unnerving to Aang, even in the face of his own powerful bending abilities.
* The Avatar State: While the Avatar State is Aang's ultimate weapon, it also presents a fear of losing control. We see Aang struggle with the Avatar State's overwhelming power and the potential for it to consume him.
* The Ocean Spirit: Though not a person, the immense power and wrath of the Ocean Spirit during the Siege of the North Pole are terrifying. It shows Aang the true scale of the power he wields and the devastating consequences of a spiritual imbalance.
Ultimately, Aang's greatest fear is not about a specific character, but rather the potential for destruction and the consequences of his own actions. This is evident in his reluctance to enter the Avatar State and his constant struggle to find balance and peace in a world filled with conflict.