Hypochlorite is a strong oxidant and bleaching agent. Why?

Hypochlorite, OCl^- is formed in the ground state of oxygen.
O-CI bond is a single bond. OCI^- has no tendency to form pi bond and also it is not stabilised by resonance. It is less stable and provides nascent oxygen by decomposition.
${\mathrm{OCI}}^{-}\to {\mathrm{Cl}}^{-}+\left(\mathrm{O}\right)$
Hence, OCl^- hypochlorite is good oxidant and powerful bleaching agent.