<prompt> Most powerful oxygen free radical is:HydroxyradicalHydrogen peroxideSuperoxide radicalBoth 1 2  <response>: Most powerful oxygen free radical is Hydroxyradical:Least powerful Reactive Oxygen species is Hydrogen peroxide.Precursor of all reactive Oxygen species is Superoxide radical.H2O2 is not a free radical but a ROS.Reference- Review of biochemistry by Rebecca James Perumcheril Pg-411 