While you forgot that O2 is technically a compound, therefore you need
special power to control that.
If it's single element, the most useful and versatile one is Carbon indeed.
1. It's used in too many compounds, should you be able to control it. From poison to food to weapon.
2. Even if you can only control -pure- element, pure carbon can be turned into graphite or diamond, for strength or if you want to plain suffocate people.
Against Arsenic? Just swallow some and absorb the poison.
Against Oxygen removal? Just take some carbon dioxide and remove the carbon. Fresh air voila!
Against metallic elements? Well, carbon shield is always useful.
Against Sulfur, carbon can filter all those filthy air too.
Against Hydrogen, just fuse them and you get hydrocarbon compounds (preferably poisonous) to counter.
As an extra bonus, you can easily get drunk too. (alcohol is C2H5OH)