Most of these characters never engaged in a fight, thus this answer isn't based on any facts. The answer is mere speculation and personal opinion.
The only battle between some of these characters that actually occurred in the series was a battle between the novice waterbender Katara and the master waterbender Pakku. In this fight, Pakku won against Katara. The result of this fight, however, isn't representational to the outcome of hypothetical fights in the future, as Katara hadn't received any proper training when she faced off against Pakku, and since then, she noticeably improved much, becoming a waterbending master herself.
In the comic "Bumi vs. Toph, Round One", Toph proves to be an equal match against King Bumi.