- Zaheer >>> someone who genuinely pursues something "good and altruist" from his PoV. Definitely Korra's greatest challenge in her road to mature as the Avatar. Not only he was a powerful bender, but his entire philosophy was necessary for Korra to stop being a "child avatar", and considering the true weight of her responsibilities.
- Azula >>> EXTREMELY charismatic, a real menace, and she gets even more endearing by the fact that she isn't just an obstacle for Aang's journey, but for Zuko as well. An antagonist that works wonders for both the protagonist and deuteragonist? Rare thing to see.
- Amon (before the bloodbending reveal) >>> a twist on the "bending is cool" theme. Amon represents a dangerous reactionary PoV that easily spreads irl, with people blaming groups of people due to "natural" characteristics, or for just being who they are. The reveal that is was all a ruse and he was some powerful bloodbending kiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiinda ruined it for me, though.
- Zhao >>> he gets high on the list for "being the first major villain in the series". Didn't have much expectations for him, but he performed his role admirably. He also served as an obstacle for both Aang and Zuko.
- Ozai and Kuvira >>>dictators with some grandiose mentality. I give the edge to Ozai due to his ominous presence during the entire of Aang's journey, but, as I've said before, he just fell short on development, IMO. Kuvira was great, though.
- Unalaq >>> really, really weak grandiose villain that lacks the little charisma both Ozai and Kuvira had. The "dark avatar" plot was pretty meh, IMO. Seeing Wan's story was cool, though.
Honorable mentions:
- Feng >>> he was a cool antagonist in Ba Sing Se, but he got majorly outplayed by Azula, so he didn't get to shine for much long. A pity.
- The rest of the Red Lotus >>>I love them, but, being realistic, only Zaheer "mattered". Ghazan's lava bending and Ming-Hua no arms water bending were cool as fuck, though. my personal favorites from fighting standpoint.
- Yakone and Sato >>>meh. Amon was the star of the first season. But Yakone had a beautifully tragic ending alongside his brother. Shed a tear.
- Hama >>> her and Koh are the scariest characters in the show.
If I forgot anyone, it's because it's been a long, long time since I've watched the shows. Not because I don't like them.