Ghostbusters: Spirits Unleashed Ecto Edition

Easy to do as long as the ghost isn't actively attacking you. Equip your PKE meter by pressing . Then, when you see a ghost, blast em by holding down . It will take a few moments to charge up and blast, so be ready to abort if the ghost is fleeing, the range is not long, and once you use your blast, it takes some time to recharge, and during that time, your PKE meter is useless. Try doing this on objects that are possessed too. The ghost will be stunned and forced out of the object.

I'm pretty sure you can also use the training ghost in the outside area of the firehouse to get this one, but I'm not certain and would love someone to confirm if it is possible.