Best Benders?
Um okay um. Saying it, no order because I can't make up my mind in terms of raw power or skill.
Airbenders: Aang, Yangchen, Kelsang, Gyatso, Tenzin and probably Jinora due to spirituality. Honorary mention to Zaheer (I still don't think he could have beat any of those in a fair fight except 11yo Jinora) and maybe Kai for being the best of the new Air Nation. Maybe Korra too, EoS Korra was a pretty good Airbender and among the best in LoK, but nowhere near the level of Kelsang is what I mean.
Earthbenders: Toph, King Bumi, Yun, Kyoshi and Jianzhu. Honorary mentions to Ghazan and Bolin because lavabending is cool and for Su, Lin and Kuvira who are great too (I still don't think they could beat any of the others I mentioned though).
Waterbenders: Noatak/Amon, Yakone, Pakku, Tarrlok, Katara, Korra, Kuruk, Unalaq, Ming-Hua-- btw can anyone explain why the waterbenders in LoK were all so fucking OP. Honorary mentions to people like Tonraq who are pretty good. Oh and Yue, I guess-- with the whole moon spirit thing.
Firebenders: Ran and Shaw. Okay, now seriously. Ozai, Iroh, Sozin, Jeong Jeong, Azula and probably Hei-Ran and potentially Adult Zuko. If we speak about potential, Azula is probably the strongest Firebender in the franchise, but she was 14 years old and I don't think she could have beat someone like Ozai or Iroh —much older and more experienced— even being a prodigy. Honorary mentions to Combustion Man and P'li (because boom, but tbh we didn't see that much of their bending skills), Show Zuko, Rangi, Mako and Korra because tbh they were all very good, too. Xu Ping An too, I guess. Zhao has good raw power too but that guy sucked at everything else.