Must be 1000 dmg with one attack to one enemy. In order to achieve this equip the "Tetsuzankou" Special Skill and the "Dying Rat" & "STR Boost" Optional Skills. Be sure to maximize both Optional Skills. Then go to the final lvl of story mode (25) and beat the huge red vortex boss over and over again to lvl up. After you think your lvl is high enough (I did it with lvl 67), start the lvl again and let the enemies hit you till your HP drops to about 5% left. (This is to get the most out of the Dying Rat skill.) Then counter a long golem with Tetsuzankou. If it doesn't hit 1000+, try again or lvl up some more.