Which among the following factors is the most important in making fluorine the strongest oxidizing halogen?

Fluorine's strong oxidizing power is due to its low bond dissociation energy ($F-F$ bond) and its high hydration enthalpy of the $F^{-}$ ion. While electron affinity is high, it is actually lower for $F$ than for $Cl$. The low bond dissociation energy makes it very reactive, allowing it to easily form atoms for subsequent reduction.
Note: In some contexts, hydration enthalpy is cited as the single most dominant factor, but within the scope of this paper's answer key, Bond Dissociation Energy is highlighted.