Its tricky, for this battle you have to use savestates in order to proceed. It is essential that you do not attack "Deus" until he uses his special move at least 3 times, for this guide to actually work. So no jumping the gun.
Remember its F1 to Save and F3 to Load a Savestate.- Step One - OK its time to start the battle!
- Once the battle has begun, keep skipping moves until "Deus" does his "Special move"(halves everyones HP).
- Step Two - Savestate just after "Deus" does his "Special move" that halves everybody’s HP.
- Step Three - Just keep skipping moves until "Dues" does his special move once again. The game will freeze at this point(If it doesn't your one lucky batard).
- Step Four - When the game freezes, hit F3 and reload your savestate.
Repeat these 4 steps again until "Deus" has used his "Special move" at least 3 or 4 times. Once you have repeated the steps 3 times or 4 times, 5000/2500 damage will be required to kill him and win the battle.
And thats it congratulation on getting through the battle
Edit: I'm unsure if this affects 1.70, please pm me and tell me if does or doesn't.
Edit 2: I can confirm that 1.70 still has this problem, Thanks to KrossX for pm'ing me on this.