I'VE HAD A THOUGHT AND ITS BUGGING ME-
Ok so say you were some kind of water bender that can use their power ONLY by touching water. (like if you touch a pool that entire pool is under your control, touch an ocean bend the ocean)
Wouldn't you technically be able to kill everything on earth? Just saying..
Water is made up of 2 hydrogen to 1 oxygen, which not only is in our atmosphere, water molecules also float around and condense daily.
So theoretically you always have control over the atmosphere (or at least part of it, a good percent)
And that means if you move or get rid of the water in the air...we're cooked.