>>14098532
>Ability to breathe in any hostile environment
Breathable air needs nitrogen too, so unless you're fine with huffing pure oxygen or combining it with whatever toxic air is nearby, you're still fucked.
>Make it harder or easier for plants to thrive by removing it
Removing oxygen does not generate carbon dioxide.
>Feed or snuff existing fires (but not create them)
this one works
>Suffocate enemies, by removing it
so does this
>Poison enemies, by concentrating it
and this
>Corrode metals, especially iron
Only if the metal has exposed, uncorroded material. Otherwise it'll corrode the outer layer but not penetrate unless the metal flakes off by itself.