Sasuke Uchiha from anime/manga series, Naruto, and Zuko from cartoon series, Avatar: The Last Airbender are two characters whose actions have bring up complicated issues. It's because of their acts, some people might confuse their alignment. In other words, which side are they on?
The question is, are they good or bad?
First, let's compare and contrast them. Both of them are mostly skilled with fire techniques. They were loners and have problems with their siblings, Itachi and Azula, respectively. The thing is, their fathers respected them more than Sasuke and Zuko, giving them a motivation of trying to earn their respect. For a contrast, it's their main goal; Zuko wants to be get his rightful place as heir to the Fire Lord by capturing the Avatar, and Sasuke wants to restore his clan by killing his brother, the one who did the deed in killing everyone in their clan with themselves being last standing.
Now on their alignment...
Sasuke is good, despite being a rival to Naruto Uzumaki. Well that's because he's also his best friend. They have such bromance moments like fighting bad guys together and working together in complicated stuff. However, his obsession of revenge could make things complicated, not to mention being granted with the curse mark from Orochimaru really restores his motivation. After being defeated by Itachi again, he tries to pick a fight with Naruto, but failed. Even Kakashi's lecture wouldn't let him forget about it as the Sound Four, Orochimaru's henchmen, beat him and tell him that his bonds with his friends are holding him back from his quest of revenge. This finally sends him over the edge as he is going to join with Orochimaru to get more power and left the Hidden Leaf Village. As of now, Sasuke is bad.
Zuko is bad, trying to get the Avatar, but ended up getting failures. In the middle of season 2, he joins up with his team, but betrays them with the help of his sister, Azula. This finally gets him back to the Fire Kingdom. However, in the middle of season 3, he begins to struggle with his duties after visiting his Uncle Iroh, who have told him that he is maternally a descendant of Avatar Roku, whose goal is to stop the war. When he ended up resulting a plan to destroy the Earth Kingdom, this finally gives him the right decision as he confronts his father about joining with the Avatar and left the Fire Kingdom, including his sister. As of now, Zuko is good.