In Rakshek Resort there is one battle(I.P.D and Sacred Soldier)which allows you to test how mush damage you can do at your current level on weak enemy.

To be able to activate that bug you must have the "Reset Button" song(not Eset Button)to be able to activate Replakia by resetting the battle(those two enemys are too weak and it's impossible to activate it on them...kill just one of them until you gain access to Replakia but make sure that the Sacred Soldier is alive when you activate Replakia).

So when you can activate Replakia,switch to some attacking song and activate it.Doing that will make the Sacred Soldier immortal(he used the Guts skill every time you hit him so he always stay at 1 hp)until Replakia end(you can't kill him with any attack even with Replakia but you can when Replakia end)

Here's the code for that song if you don't have it yet or not playing the Closche route or already have the "Eset Button" which it extremely stupid song magic(this code removes the "Eset Button" and add the "Reset Button" "but if you want it again just add 7 at the end of the value)

Quote://Reset Magic
patch=1,EE,10BE6B7A,extended,00000700

PS.I'm playing on my PS2,this is not bug with pcsx2