What Shin is referring to is a glitch known as the Kiss of Blessing, which is essentially tantamount to cheating. Kiss of Blessing occurs by Mixing a Maiden's Kiss and a Revivify/Holy Water. It causes Haste, Image and Berserk on anything, even if that target is immune to any or all of those statuses. Berserked enemies completely ignore their normal AI scripts, which completely removes any semblance of challenge from Omega. Because it screws with the AI scripts, it prevents the Neo Ex-Death battle from following Ex-Death. It also affects Gilgamesh battle events, and can allow one to fight one-time enemies like Catoblepas more than once.