O2 has more discharge potential or OH has more discharge potential???

The two ions that u have asked are actually anions. These will get oxidized at anode during electrolysis.

Here the discharge potential in this case is actually the oxidation potential. The ion having greater oxidation potential will get discharged earlier at the anode.

Taking in view the Standard Oxidation Electrode potential of the ions, it is clearly inferred that OH- have relatively greater oxidation potential than O2-

Therefore, O2- have less discharge potential than OH-

Let me also clarify the hypertalked Electrolysis of H2O. Here, H+ having greater reduction potential is discharged at cathode.. At Anode OH- should be discharged not O2-. But due to ‘overpotential’ O2- is oxidized to O2 not OH-