You shall be able to find the most correct answer in the following article.
http://en.wikipedia.org/wiki/Oxidizing_a...
Oxidizing agent gets reduced, but it oxidizes something else. Similarly in the case of reduction - reducing agent reduces something, and it gets oxidized in the process.
Fluorine oxidizes almost everything - so it is a good oxidizing agent.
The most powerful oxidant will have the highest standard reduction potential.
fluorine (f2 on periodic table of elements)
By definition, it is oxygen.
