They are ghosts, who have had some great wrong done to them in their lives (normally what killed them), this causes them to remain after death, to try and avenge this wrong. Over time they slowly become obsessed with this until it is the only thing they can think of. Bobby described it like "an itch that you just can't scratch". As such they act violently to try and avenge the wrong, however in the process, their obsession with revenge often leads to them harming innocent people. Sometimes their vengeance can spread on to others, who had nothing to do with them, but have or are doing something that is similar to their death.
It is possible that once they are avenged they pass on, however often they are unable to cause this. Occasionally, they're people who are still alive, but on the verge of death.
To kill a vengeful spirit you must find the body, salt and burn it. If the body is already burned then the spirit is possessing an object. Once you know what object it is possessing then you salt and burn that.
Scepters are particularly vengeful ghosts that are less focused on personal vendetta, like most vengeful spirits do, and more on the concept of vengence. They are powerless as themselves, and can only act when possessing an individual. When they do so, they focus on this individual's repressed resentment and feeling of revenge, amplifying them to such degree the possessed individual is forced into violantly following this resentment/revenge, which generally ends up in them murdering whomever they hold grudge for, be it the slightest.
- Peter Sweeney - Takes revenge on those who drowned him and their families, passes over when the final killer gives his life to him, thus avenging him.
- Mary Worthington - Kills people, who are, or believe they are responsible for others deaths, as in her death her killer was never captured. Dispatched when forced to look at her own reflection, as she was responsible for many deaths, forcing her to destroy herself.
- Cyrus Dorian - Takes revenge on those responsible for his death, and their families. Dispatched when lured onto holy ground, thus forcing him to leave.
- Maggie Thompson - Kills people, who are connected in some way to the sale of her home, the Pierpont Inn so she wouldn't be alone. Her spirit still lives in the inn with her sister Rose after Rose offered to stay with her when she died so Maggie wouldn't be alone.
- Father Thomas Gregory - Killed on the church steps, for his keys, returns thinking he was an angel, he went to those who had nothing, and rebuilt their faith, but also had them kill people doing evil deeds. Was put to rest when his fellow father, convinced him to stop.
- Jonah Greely - Attacks drivers, as he himself was killed in a car crash. Dispatched when Sam, salts and burns his corpse.
- Callie Garrison - A very powerful ghost, following years of building anger at her father not letting her die, and her not knowing it was her stepmothers fault. As such started bringing the fairy tales he read her to life. Passed over when he accepted the truth, and let her die.
- Sailor's Ghost - Killed those, who killed their own family, as he was killed by his own brother. Appears every 37 years, to mark his age when he died. He was dispatched, when he attacked the summoned ghost of his brother, causing them both to be destroyed.
- The Witnesses - Raised by the demon Lilith, they attacked the hunters who failed to save them. They were all dispatched by a spell.
- Dirk MacGregor, Jr. - A victim of bullying, after being overthrown, he returned and possessed others causing them to attack their bullies. He was dispatched when his last lock of hair was burned.
- Rose Brown - Took revenge on her colleagues, who bullied her in her life and led to her death. Dispatched, after she accidentally killed her sister.
- Jo Harvelle - Made a Vengeful Spirit, by the Egyptian god Osiris, who summoned her from rest and forced her to attack, and try and kill Dean, in a manner similar to her own death. Once Osiris was defeated, she was free from his control and passed on for a second time.
- Other Unnamed Spirits - Summoned by Osiris, to kill those who were declared guilty. They each passed on, once their target was killed.
- Lara Coggins - Left at the aisle on her wedding, she slit her throat, and took revenge on all men who broke women's hearts, by grasping their own hearts and squeezing them, until they died. Was dispatched by Bobby and Rufus.
- Howard's brother - Summoned by Dean using Howard's Fear Manifestation Ritual to embody Howard's fears of drowning and his brother blaming him for his death. Drowned Howard from the inside with a touch.
- Marin's Brother - Older brother of a young woman named Marin. While originally only haunting his sister, he appeared to become vengeful out of loneliness and began targeting Marin so that he wouldn't be alone. Dispatched after Sam burned Marin's bracelet which he was attached to.
- Bobby Singer - Following his death at Dick Roman's hands, he returned as a spirit, but his anger towards Dick, continued to grow, turning him into a vengeful spirit, unable to control himself he tried to kill Dick, and anyone who got in his way. However his humanity was reached, when he almost managed to kill Sam. Realizing what was happening, he returned to the brothers, and told them to burn his flask, as he knew he would soon lose control again. They did, and he was dispatched.
- Vance Collins - aka the southern Unknown Soldier, an American civil war Confederate soldier. After his brother, who was a union soldier, killed him, he returned as a specter, a particularly vengeful kind of ghosts. He possessed several people and forced them to act according to their repressed resentments and kill those they held grudge for. Was put to rest by Dean Winchester and Garth Fitzgerald IV, who melt the coin he was attached to.
- Andrew Silver - Killed in a car accident that was the fault of four young college students. Using the Internet to move around, Andrew sought revenge, killing three of the students before his wife, Corey, convinced him to move on peacefully.
- Isabella - A nun who in 1520 fell in love with a man named Piarro who painted her, using her blood and ground up finger in the pigment of the painting. After Piarro rejected her and she found him in bed with another woman, Isabella brutally murdered him and was burned at the stake as a witch. Came to the United States when her things were sent to a church in Massachusetts and began murdering unfaithful men. Put to rest when Sam salt and burned the painting.
- Chester Johnson - A man who was accused of child molestation and accidentally killed by the men accusing him. Came back for revenge by possessing the various costumes he wore in life as a children's performer. Put to rest when Sheriff Donna Hanscum, her deputy Doug Stover, and Sam burned the various costumes.
- Fiona Duncan (alternate timeline) - The fiancé of Gavin MacLeod who became a vengeful spirit after Gavin was displaced to 2014 by Abaddon and wasn't there to protect her from being brutalized by the crew of the Star. Wished for revenge against teachers as her own teacher had encouraged the crew's treatment of her rather than protecting Fiona. Killed four people before the truth was discovered. Fiona's existence as a vengeful spirit was negated when Gavin returned to 1723 and protected her on the Star. In the restored timeline, Fiona's victims were all alive and well.
- Ghost Kid - A young boy who died of unknown causes and who was used by Jay for his own personal gain. His situation caused him to lose control and attack people out of anger. After sucking the Winchesters and Castiel into an episode of Scooby-Doo, Where Are You!, he was put to rest by Sam when he melted the pocketknife he was attached to with a blowtorch.
- Jordan MacNeel - The original owner of Smash! Pow! Collectables comic shop, and was known for being over-protective of his belongings. He had a turbulent relationship with Stuart Blake who often stole from him. Jordan passed away due to complications with his cancer, but became a vengeful spirit after Stuart was continuing to steal from him.
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