Because I prefer my evil to be chaotic, destructive, cruel and unwarranted, I will boldly say Vaatu is my favorite Avatar villain. Fueled by a primal, natural desire and nothing else, he embodied what many shows attempt to and fail at. However, in comparing Amon and Zaheer (and/or Red Lotus), I would have to side with Amon. I dislike the spiritualistic capabilities of Zaheer, and despite my highly-rebellious nature, I'm far from an anarchist. I didn't agree with him, I didn't follow his logic and, as someone whom normally roots for and sympathizes with the villains, I felt no remorse for Zaheer. At that, the Red Lotus pissed me off for several reasons, first and foremost being that no one aside from Zaheer even adhered to its principles. Unalaq was using the Red Lotus, and at that acted without the assistance of others. Ming and Ghazan were criminals, not really seeing true anarchy as much as they were merely siding with whomever offered them redemption/freedom. P'Li was in love with Zaheer. But, the characters are never embellished on after that. You don't get to 'feel' their motives or understand why or truly comprehend their depth as characters; they're all just benders with a unique bending style and a desire to dissolve world order. Amon was far different. With Amon, there was depth and a definite plot and it introduced us to the setting and the new politics and the new aspects of being an Avatar. It also showed us the innovative new ways bending can be used as people adapt to it in harsh,. harsh circumstances. Not to mention, I'm a larger fan of smaller plots that don't involve world domination/destruction/revolution/alteration. The ending to the first season had a powerful sense of catharsis and just made the setting the darker version of Avatar that it is.

Needless to say, Season One of Legend of Korra is my favorite by far. I believe its writing is definitely the best and its the most down to Earth.