In order to unlock this achievement you must earn an A ranking in all levels including the remix levels which unlock following the final boss.
Your rank is based on the total ectoplasm collected during a level.
The standard levels won't pose much of a problem however the remix levels are a little trickier.
The key to this achievement is exploration. Use your radar and hold down on the B button, the b button shows the main path so if you see any areas which open up and lead away from the main path explore them.
One of the best sources of ectoplasm inn every level is environmental destructibles you can earn between 30-50k just by destroying these.
Also ensure that you have the multiplier extension and trap reward skills fully upgraded. Make sure you kill all on-screen enemies, usually when last one killed a trappable ghost appears.
Don't be fooled by cones. Many areas appear blocked off cones just shoot these cones and explore.
You should be aiming between 250-300 On the remix levels
If you fail remember what your score was and while replaying the level keep adding up your scores to ensure you beat the last total