"Got to Nene Before Bomb Went Off" achievement hint
To get this achievement easily while defeating all unique enemies on this airship, make sure one of your characters has field barrier. Start each floor by defeating the two or three characters that are unique, then activate your field barrier. You will not have to kill them again. Bouncing into them and instantly killing them costs no time, while a regular fight takes about thirty seconds. It will be easy to complete this level in about 40 minutes.