Translation: Force Enhancement
Extend increase in score for more bombs. (Story mode, Solo Play)
You must reach a high enough score to be rewarded with an extra bomb (3,000,000 points). I received this achievement just as i destroyed the second boss with a bomb, while playing as the fourth character on very easy. I had not used any continues up to that point and destroyed pretty much everything i encountered since this character has auto-targeting shots.
You can also put the No Damage setting on if you like and you should have no problem. Be careful as you can still die by touching enemies, but you will be immune to all types of shots.