Warning: Much of this is fucked up, potentially triggering stuff. Please don't include anything from this list in your game if your fellow players are not okay with using this kind of material.
- You used to kick the family dog when no one else was around.
- Once when you were walking through the woods, you found an injured baby bird. You killed it with a rock. You told yourself that it was to put the poor thing out of its misery, but you really did it because you wanted to.
- You have a friend who fantasizes about being sodomized by your local clergy. You found out about this by reading their diary or spying on a private conversation they had. Sometimes when you are alone with this friend, you mock them about it mercilessly. They seem to be afraid to stand up to you about it.
- When you were 12, you were playing on a frozen lake with your older brother, who was better than you in every way. Your brother fell through the ice. As you were moving to help, you hesitated because of a stray thought: you would be happier if he were dead. He did indeed die.
- You used to bully one particular person ferociously. They used to be skinny, but over the years they gained a lot of weight, their hair turned gray prematurely, and they started to get sick very often. You can't shake the feeling that this is your fault.
- You stole your best friend's prized possession. They never found out it was you who took it.
- You wrote a full diary's worth of vivid descriptions of your loved ones being tortured and brutalized.
- You used to take care of your friends' very young son when they were out of town. You habitually and purposefully put the child's shoes on the wrong feet when you dressed him. He eventually developed trouble walking due to skeletal deformities in his feet.
- The last words you ever told your mother before she died were "I hate you."
- You convinced a friend who usually abstained from alcohol to get blackout drunk one night. She then slept with someone while in this state and became pregnant with a child she could not afford to raise by herself. She does not remember who the father is.
- You stole money from your parents when they needed it most.
- You gave your friend a piercing, tattoo, or other piece of body art that got badly infected. They ended up losing a body part.
- You killed someone in a hunting accident.
- To pay off your gambling debts, you once stole a lot of money from a church.
- You once reported to the authorities that a vagrant was scaring you, even though you knew he did not mean you any harm. The authorities did not take kindly to this. They beat the vagrant so badly it crippled him. You could never look him in the eye when you saw him begging after that.
- You found out an important local figure was having an affair. You used this knowledge to blackmail him for money. After several months, he killed himself.
- Your father used to beat you severely for minor, unintentional slights. You got fed up with this and tripped him down some stairs. He hit his head. Now he has trouble talking and feeding himself.
- When you were 10, there was another child you know who would swell up and get sick when she ate a certain food. You thought this was really funny. You slipped some of this food into a meal she was eating. The allergic reaction killed her. You never confessed to poisoning her.
- You accidentally burned down your family's house, rendering all of you homeless and penniless. No one ever found out it was you who started the fire.
- You and a group of other children accused an innocent person of a crime for fun. The charges stuck, and they were severely punished by the law.
- You used to spit in people's food. You only quit because you were almost caught once.
- When you were 13, one of your peers beat you up. To get even with them, you killed their dog.
- You started a false rumor that one of your peers was a sexual deviant. They are now shunned by the community.
- You lit a cat on fire for fun. It was hilarious.
- Whenever you need extra money, you mug a stranger. So far, you have gotten away with it.
- You used to have a lover or significant other. Over time, you slowly convinced them they were going insane.
- You have a history of sleeping with other people's spouses.
- You like to slip drugs into people's food or drinks and watch them make fools out of themselves in public.
- Your favorite hobby is breaking and entering.
- One time, you started a bar fight in which an innocent bystander ended up being beaten to death.
- When you could no longer afford to take care of your pet, you abandoned the animal in the wilderness to fend for itself.
- You made a lot of money selling illegal drugs to children.
- You stole money from a homeless person.
- You literally stole candy from a baby.
- You borrowed a lot of money from a loved one so that you could start a business. The business was successful, but you have refused to pay back the money you owe.
- When you were 14, you caught your sister having sex with an unpopular local figure. You threatened to tell on her if she did not obey your every whim. When you got bored of blackmailing her, you told on her anyway. Your parents did not take it well.
- While hiking, your friend fell and was badly injured. They could have lived if not for your incompetent attempt at first aid, which injured them much more severely.
- You enjoy deliberately polluting water upstream from people who are drinking from it.
- You cheated on your spouse by sleeping with a prostitute. Your spouse does not know, and you remain happily married.
- When your significant other became chronically ill, you broke up with them.
- You made a lot of money from dogfighting or cockfighting.
- When you were 7, a family member tried to teach you how to use a weapon. You accidentally killed them with it.
- You know how to hit people without leaving any obvious marks. Whenever you are alone with a child and think you can get away with it, you smack them around. Their parents tend not to believe them.
- You have gotten very good at spying on people while they undress or bathe.
- You have an employee whom you pay far less than a fair wage, because they do not know better or they are simply desperate enough to tolerate it.
- During your first tryst with a new lover, you misinterpreted something they said as making fun of the appearance of your naked body. In a rage, you beat them to a pulp.
- You once tricked a very devout member of a minority religion in your community (which you do not share) into breaking a commandment or committing a taboo which would be minor or nonexistent for you but gravely important to them. They were publicly disgraced for this action.
- You took advantage of someone's weakness for gambling and took money from them that they desperately needed in order to keep their family clothed and fed.
- You made a lot of money as a pimp. You were not a nice person to work for.
- You tricked an elderly person into giving you the majority of their inheritance under false pretenses, even though their family deserved it.
- You once prayed for someone to die. A short while later, they did.
- On a dare, you once put a dangerous animal in someone's house. You did not know that a child lived in that house. The animal killed the child.
- You are a very trusted person in your community. Many people tell you their secrets because they trust you to keep such information private. You secretly write down everything they say.
- Your friend was accused of attacking someone in your neighborhood. Your friend was guilty, but you lied to corroborate your friend's false alibi. Your friend was not convicted of the crime.
- Your favorite hobby is to find strangers walking alone at night and beat them up. You don't even rob them. You just enjoy the violence.
- You treat your family with utter contempt, far beyond anything they might deserve.
- As a child, you used to catch small animals and kill them slowly.
- You sell alcoholic beverages to people who are too young to safely and/or legally drink.
- You have a friend or family member who you constantly belittle for their appearance and intelligence, because it makes you feel better about your own failings.
- You have a strong sexual desire for one of your siblings. You have purposefully spent less and less time around them over the years because you are afraid of showing your true feelings.
- You vehemently criticize and verbally abuse homosexuals and other so-called "perverts" in order to hide or deny your own atypical sexuality.
- You like to tear random pages out of books that don't belong to you.
- One time, a stranger asked you for directions, and you deliberately gave them wrong information. You later found out they were murdered at the location you sent them to.
- You lied to an acquaintance about their spouse cheating on them, causing their marriage to break up.
- You and several other violent thugs used to charge local businesses for "protection" and hurt them or their property if they didn't pay up.
- You sacrificed one of your children in a religious ritual.
- Your fascination with fire led you to burn down several houses when you were a teenager.
- You pushed someone down a well and left them to die.
- You and one of your siblings have a romantic, sexual relationship.
- You have a friend who likes to kill people. You help dispose of the bodies.
- The secret ingredient in your popular pies is human meat.
- You hide traps outside of town, hoping that people will stumble into them.
- When you were 13, you blinded your friend with cooking grease. Everyone else thinks it was an accident. It wasn't.
- You kidnapped someone and kept them locked up because it was the only way you could get them to "reciprocate" your love for them.
- You only hire employees that you find attractive.
- You led a moral crusade to ban a substance in your town which you deemed harmful. This ban led to the imprisonment of someone you loved dearly.
- You helped run a family out of town simply because they were foreigners.
- You stole money that was meant to be donated to people who are sick and poor.
- You were part of a lynch mob that executed an innocent person.
- You murdered a family member for "dishonoring" your family.
- You went to great lengths to provoke a normally non-violent enemy into attacking you so that you could kill them in "self-defense."
- You dared a friend to jump off of a building. They messed up the landing. Badly.
- You slipped a drug into a competitor's drink to make them sick so that they would fail a test for a promotion. You got the promotion instead, even though they deserved it and you did not.
- You have a collection of stolen undergarments.
- You like to steal food from other people's gardens. You're not starving or anything. You just like getting free food.
- When you were 15, you vandalized a church. The crime was pinned on a group of young people who belonged to a religion that was unpopular in your town.
- You have a monopoly on the sale of a certain important good or service in your town, and you charge far too much for it.
- You let an acquaintance live at your house when they had nowhere else to go. You then pressured them into sleeping with you.
- There is a young widow or widower in your community who does not have the means to survive without help. You give them enough money to get by every month, on the condition that they have sex with you. They do not have the luxury of refusing this arrangement.
- When you were 11, you and a younger cousin went to the barn alone to play doctor. You "showed them yours," but they "chickened out" and ran away when it was their turn to "show you theirs."
- You talked someone into committing suicide when they were depressed.
- Under the guise of generosity, you deliberately gave someone a blanket or clothing infested with fleas or bedbugs.
- You secretly sold weapons to both sides in a conflict.
- You used to be part of an illegal underground fighting ring. If you were a fighter, you killed at least one person in a fight. If you were running the ring, you were responsible for failing to stop at least one fight that became lethal.
- You saw someone drop money on the ground without realizing it. You could have pointed it out to them, but instead you waited until they left and then kept the money for yourself. It turned out to be a lot of money.
- You once murdered a police officer or other authority figure to prevent them from turning you in for another crime. You got away with everything.
- You caught someone stealing a small amount of food from your business in order to feed their family. Even though you knew they were just doing it to survive, you turned them in to the authorities. They received a harsh sentence.
- You were paid to murder someone's cheating spouse.
- While travelling, you came across someone who was stranded in a dangerous place. You moved on without offering any help because they were not the same race/ethnic group/nationality/religion as you.
- You murder lots of people and do arts and crafts with their body parts.
A non-exhaustive list of inspirations for this post: Fall Out Boy lyrics, the novelization of The 7th Guest (Yes, this exists, but as of this post I'm not done reading it yet), Blade Runner, Sweeney Tod, Antichrist, Gantz, the Silent Hill series, The Hateful Eight, Les Miserables, Gas Light/Gaslight/Angel Street, and a bunch of stories about serial killers.