A Class 7 Entity (that is part of the Classification System) are gods and demons, and are very powerful.
Taken from Ghostbusters Role-Playing GameEdit
Class VII: Metaspectres. Obsessively malevolent, exceptionally powerful, and exhibiting control over subordinate forms, such entities are potentially very dangerous. These are often identified by primitive cultures as "Demons". Entities which fit this classification include Gozer, Vinz Clortho, and Zuul. Neutralizing them is usually a problematic undertaking at best. Most standard procedures are futile. The most realistic plan is to take measures to prevent these things from entering this sphere of influence in the first place.
List of Spirits/Ghosts based on The RPG GuidelinesEdit
Animated Series Class 7Edit
The animated series doesn't follow the same rules as RPG and can go higher. To read more about it go to Animated Classifications.