In this video guide I will show you how to wield overwhelming power to exact an unexpected conclusion. So to do this you need to beat the boss in the prologue. I would recommend having Nero's Devil Bringer upgraded to finish this with two blows once the shield is down. Also doing this on human will be a lot easier. Just use Nero's mega blaster and guns from a distance to break the shield. Once that is down go up to him and activate the Devil Bringer and press RB+Up with left stick and Y+B. Use this move twice and he will be dead. Once the results screen shows up your achievement will pop.