Record of Agarest War Zero
44 Achievements
189-231h
Better Safe Than Sorry
Overkilled 500 enemies.
12.9%
How to unlock the Better Safe Than Sorry achievement in Record of Agarest War Zero - Definitive Guide
If you're against buying DLC, the same method works, but you may want to hold off till you're near level 25 or so, just to make it easier on you. This way you should have pretty good gear, more party members and higher stats.
Some decent options:
Inicio Plains, North
Laifulle Plains
Claruine West Way
You'll also build up a non-trivial amount of TP while you're at it. I was getting ~6 per battle.
An Overkill is when you inflict basically the same amount of damage as the enemies total health after the "finishing" blow causing an OVERKILL which will pop out noticeably big letters above of the enemies health display on the bottom left corner. So long as you plan out your finishing moves properly this should unlock naturally by the end of generation 2. Overkills in auto-battle DOES count towards your overall total so if you purchased any overpowered DLC weapons you could set the battles to auto battle by pressing and letting the CPU get all the overkills for you, when the CPU is in command of your party they tend to go all out even on the weakest of monsters.
Those. if the enemy has 100% health, you need to hit at 200%. If there is 10% health left, you need to hit 110%...
Repeat 500 times throughout the game.