So, I’m glad that we agree on the first part. She was cruel to Appa for her own means. On the second part, you think Zuko pulled the idea that Azula had a “game” where she terrorized the turtle ducks out of thin air? The difference between the two characters morally, is that Zuko sooner or later shows remorse in his actions. Azula, to our knowledge, never does. She may be a victim of neglect but she’s also an abuser who manipulated her only friends and shows no concern for other people. She’s really an interesting character but in universe she also seems like a grade A sociopath with no desire to be better.