Im quiet interested in such stuff and eager to share some of the more obscure Grimm-tier ghosts of our folklore.
You can basically part them into dangerous apparitions that were once pagan gods/spirits and then got devilified after the arrival of Christianity, ghosts made from people who failed oaths or blasphemed the lord and got punished this way and then bodies of deceased ones who still hold the soul in them due to unproper burial and paratize on the living in some way.
That last one is found in most european countries and seems to be a belief transmitted from the antique.
An example for a most likely pagan concept turned into a spook is the Roggenmuhme.
A wrathful female spirit that lives in rye fields and appears as a towering old hag with coalblack or pale white skin, her heart and nails are made of iron and she is covered in a multitude of tits made from various materials such as wood, iron, glass and silver which excrete poison, blood or tar.
She is able to transform into animals or the wind.
She lives under the earth below the ryefields and often appears at noon and while she claims a part of the harvest as her food she also fertilizes the field by her presence while punishing or favoring the peasants to her liking by making their work harder or easier.
The Roggenmuhme seems to really fucking hate children though.
Children who run through the ryefields alone are prone to getting catched by her, which usually ends in most terrible torture and death, such as various forms of mutilation with shears and sickles, getting squashed in a churn, devoured or forced to suck her poisonous tits.
Other weird ghosts based on prechristian influence are the numerous kinds of dwarfes in german folktales which are often helpful if treated fairly but can vanish or perish under ridiculous conditions, such as the Heinzelmännchen of Cologne who agreed to do work at night under the condition that noone left the house to see them at that time, or the Moosweiblein (Moss-girls) hairy little female cobolds hopping through the woods helping travellers for food but die if fed caraway.
Ghosts made from people who failed oaths or blasphemed can be similary bizarre.
Such as the Muhkalb, a ghost appearing as juvenile cow with burning eyes and an oversized head howling loudly at night and spreading terror.
In one case it was said to be a perished Butcher who sold dog-meat as cow-meat and denied all accusations by swearing to be born again as a cow should the rumours be true.
Also Aufhockers who lurk in the woods at night and hop on peoples backs in order to rush them to death or exhaustion by forcing them to run, getting heavier if the vistim curses, sometimes with the goal of leaving a forest or place they were bound to by a curse.
I remember being told such a story as a child in a village in my range-Schweinheim.
Then there are the corpse based ghosts, such as Nachzehrers, basically people in medieval times believed that corpses of evil and unloved people would curse their relatives with illness and nightmares from the grave, so you had to bury the corpsee head down or drive nails in it.
People believed such tales literally up into the 18th century until the great secularisation and the spread of education and literacy which led to the tales of the spooks getting passed on not as a belief but as a mean of identification for a village community which could pride itself on an own story which sometimes got immortalised in small monuments.
The few germans/europeans that believe in ghosts, often do so not in a local folcloric sense, but by the overaching western/american way to imagine ghosts now, the Poltergeist (deep-but-loud-noise-ghost) being an exception that made it into american/world-culture due to its simplicity.