I know a lot of people are gonna bring up Toph not being in her prime, however, we never actually see her reach that point, so, therefore, Bumi and Kuvira are the top two for me, but I think that it's safe to assume that Toph would be the best in those two categories if we were to actually see her as an adult.
Catalyst1999 wrote: and toph aged 90 could rip apart kuvira's army and kuvira was schocked after Top earthbended.
The creators themselves confirmed that Toph wouldn't be able to beat Kuvira in a fight, 90 year old Toph is definitely not agile enough to doge Kuvira's quick strikes. A 12-year-old toph is not skilled enough in metal bending to beat Kuvira.
^This. Besides there already being a number of "King Bumi vs. Toph" threads as it is where I already said my peace (TL;DR: 112yo. Bumi's both in better physical shape than 80+yo. Toph and better resolve considering how bitter the latter became), I'm "Whaaa?"-ing over the idea that Chin the Conqueror because
1. His "battle" is depicted more comedically to really say it's an "accomplishment" he stood there (from a distance) while his armor got blown off
and 2. As a further precursor to Kuvira, Authority doesn't necessarily Equal Asskicking as much of her power was through politicking to have that army/cult of personality, she didn't try to take on a past-her-prime Toph and neither Chin or Kuvira ever are depicted bending on a "Super" level the way Bumi, Toph or the other Big Bads are like Amon's level of bloodbending. She's "just" better than Suyin on a marginal level instead of the kind of "superhero"-level damage one would expect from someone that touted when it was actually The Colossus being the real threat. Hell, Korra was deliberately holding back during their final fight! Besides factoring in how bending techniques have improved over the ages, Chin isn't actually even doing anything in terms of bending and likely wouldn't be doing anything on the level beyond your average earthbender grunt that Aang had to deal with.