Question

Which is the strongest oxidizing agent?

Answer 1

If one reagent during a reaction contributes oxygen, extracts hydrogen, or extracts electrons, it's said to be an oxidant. Of course, it's reduced within the process. Since oxidation and reduction are symmetric processes, always occurring together, there's always an oxidant and a reducer within the reaction.

Complete answer:
Among halogens, fluorine is the strongest oxidizing agent. it's highest value of oxidation potential. It's thanks to its low heat of dissociation and high heat of hydration which have quite compensated for the lower value of electron affinity.
Spontaneous oxidation-reduction reactions convert the stronger of a pair of oxidants and therefore the stronger of a pair of reducers into a weaker oxidizing agent and a weaker reducing agent. The very fact that the subsequent reaction occurs, for instance, suggests that copper metal may be a stronger reducer than silver metal while the Ag+ ion may be a stronger oxidant than the Cu2+ ion.
On the idea of the many such experiments, the common oxidation-reduction half-reactions are organized into a table during which the strongest reducing agents are at one end and therefore the strongest oxidizing agents are at the opposite, as shown within the table below. By convention, all of the half-reactions are written within the direction of reduction.

Note:
If oxidation of some substance is to the desired end, then it's useful to seek out an agent which can readily accomplish the oxidation. Useful oxidizing agents are bleaches and antiseptics. Not so useful is the action of oxygen within the air within the corrosion of metals by oxidation.