I did this using The End garment grid, which you will receive from Shinra after completing Shinra's Bestiary (not the one in the fiend arena). After the bestiary is complete, re-enter it for Shinra to give you the grid.
The damage you can do with this grid is dependent on how many times you've escaped in battle. The more you escape, the weaker it is, so i used it on the very first fight of an NG+ on Mt. Gagazet (you can't change your grid during the LeBlanc sequence at the beginning). Put whomever has The End all the way around the grid, and the attack Finale will appear in your list of possible actions. Use Finale for 99,999. Paine was level 3.