Third season, when Yamawaro gets fungus-juice applied to his back, which then grows a patches of mushrooms on his back. May also be counted as Squick.
Some of the going-to-hell sequences (Episodes 1 and 17 of Futakomori come to mind) fit this to a T.
The second episode of the first season centers on a teenage girl who is the victim of a stalker, which can be horribly uncomfortable for anyone who's ever been in a similar situation. The way her stalker sings her nursery rhymes on her answering machine will turn your blood to ice.
The worst part? The cops have no way of helping her. Because her stalker happens to be the goddamn chief of police.
The star of the high school baseball team ends up dying from getting a bat to the stomach. And it's not instant, either - his grieving mother recounts, in chilling detail, how he wailed and screamed about the pain as he slowly succumbed to internal bleeding.
A chapter in the manga's third incarnation is about a girl being harassed by a postman through her late grandmother's parrot. It somehow still stays scary despite the premise.
Some of the Hell banishments in the live-action series are pretty nasty, too. They include such delightful things as a guy getting crucified with wooden stakes and someone getting hanged from a staircase.
The premise of the show is pure Paranoia Fuel: No matter who you are what you did or didn't do, there will be someone out there who hates you; and could be someone out there who hates you enough to do terrible things to you. And you might not even be better than them.
You can also be sent to hell because some student who isn't quite keen on losing the attention she's getting and actually believes a lie that you're stalking someone, who then snaps and pulls the string before Hell Girl can even finish the End User License Agreement.
Hell, as the first season establishes, you can be sent to hell by some rando you don't even know just because he can. Anyone can fall victim to hell correspondence, at any time, even if they didn't do anything wrong.
The show also has flashes of what the fates of the people who contract Hell Girl's assistance will be - namely, what their punishments will be when they are finally sent to Hell themselves for pulling the string. Granted, they happen fast, but they are horrifying when you can make them out. Case in point - in the first season, a baseball player uses the string to send The Ace on the team to Hell for injuring and killing his friend. When the user dies, the rest of eternity will feature him being Impaled with Extreme Prejudice at various points throughout his body. One of them being through his face.
The other ones are pretty unpleasant too, consisting of the clients getting attacked and torn apart by disembodied hands or other damned souls, drowning in a river of blood or being sent to your classic Fire and Brimstone Hell.
The Two Prisoners involves a guy who dumped his pregnant girlfriend, who then decides to send him to Hell. His torture? Being slowly drowned in amniotic fluid while a giant fetus floats next to him. As if this isn't enough, while on the ferry to Hell his stomach is very swollen and something appears to burst out of him Alien-style.
For some, the most horrifying part of the show is not Hell Girl herself or any of the punishments she inflicts, but the atrocities committed by ordinary people that drive their victims to send them to hell.
A high school girl blackmails her classmate and frames her for stealing class money. This was after following her bully’s demand to pull a Compensated Dating as a means to earn the money back as long as the bully wouldn’t rattle her out, but the bully outed her to the principal anyway For the Evulz.
A circus worker sabotages her twin sister's performances so the ringmaster who happened to be their father, will brutally punish her and she herself can live in luxury as their father’s favorite.
A veterinarian only treats the pets of rich people and leaves one girl's injured dog to die.
A woman accidentally sees her neighbor cheating on her husband, so the neighbor harasses her, gets her daughter to bully her neighbor’s daughter at school, and sends a man to rape the neighbor. Then takes photos as proof and threatens to have her daughter raped should she reveal anything to anyone. The woman’s husband has the gall to berate her for getting in their neighbor’s bad side just cause he got a bad day at work no thanks to their neighbor talking to her husband, while refusing to let his wife tell her side of the story. Throughout the ordeal, The neighbor feels nothing but joy at ruining the lives of an innocent woman and her daughter for the mere crime of catching her in the act. This bitch definitely had it coming.
Another woman forces a girl to become her slave by holding her beloved dogs hostage, and then kills the dogs and their puppies even after the girl did everything she wanted while agreeing not to harm the dogs unless she followed her demands, yet did so anyway out of spite. But why did this woman do such cruel deeds? Because once the police storm in due to hearing the poor girl’s screams over one of her dog’s death, they discover that the woman had buried her parents and her own child in the backyard, which the girl’s dog had wandered into in the past, thus driving the woman to have assumed they have found out what she did. The bitch killed her own family because she wanted to keep their riches and inheritance all to herself. If that’s not bad enough, her victim then discovers the drowned corpses of her dog’s newborn puppies, then sends her tormentor to Hell after she’s arrested and taken to jail.
An actress's daughter cripples her rival by hiring thugs to force-feed her acid in a dark alleyway.
The people of Ai's village sacrificed her and her parents, burying them alive and forcing her beloved cousin and Only Friend to participate in the ritual because they blamed him, and her, for a famine that was making the village starve.
Even after all the atrocities mentioned above, we're shown that some people are willing to condemn themselves to damnation after death, so they can send someone who unintentionally wronged them, wronged them but since repented their action, or even someone completely innocent to hell for petty and/or stupid reasons (Episode 23 of Season 1 established that this happened horrifyingly frequently). Maybe in this world, Humans Are the Real Monsters after all.
