The Southern Raiders is in my Top 5 episodes list. It's not just because it's shockingly dark (off-screen murder, attempted murder, violation of another being, vengeance quest), but it's done in a way that completely jives with how these characters work.
- Zuko would absolutely enable Katara's darker tendencies, with his need to be accepted and forgiven.
- Katara would absolutely resort to anything to track down the person who destroyed her childhood.
- Aang would naturally object to the path that Katara embarks on, but would trust her to pull back.
- Katara would never be able to do what Aang does and forgive those who took away her family, but would have the capacity to forgive Zuko.
- Zuko would totally call Aang out on his peaceful, non-killing stance, having confronted his genocidal father.
The villain being a pathetic shell of a man was such a great subversion of what one would envision the killer to be. That scene at the end - the rain, the music, the composition - damn. I can still remember it after all these years.