Fatal Impact Achievement
Proof of dealing damage so great that it goes beyond all reason or expectation.
You need to deal more than 99,999 damage points for one single hit. This can be achieved by using strong one-hit abilities, and equipping good weapons for Lightning.
The enemy Gurangatch (a yellow shelled-lizard appearing in Yusnaan and Dead Dunes) is a good enemy choice for this achievement, because after staggering, its resistance to all kinds of attacks drops to Weakness, leaving it very vulnerable for high damage output.
Also, if you have the DLC Cloud garb, its ability is Heavy Slash Lv.2, which is an incredibly powerful move at the beginning of the game, and can easily deal more than 99,999 damage if the enemy is staggered.