This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / American Horror Story: Coven
Madame LaLaurie's attic where she tortures and imprisons her slaves
One slave had his eyes and mouth sewn shut, and it was heavily implied that she forced feces into his mouth before having it sewn shut.
Another slave had the skin of his face removed.
LaLaurie having a newborn slave baby bled for ointment to get back at her husband for cheating on her with a slave girl.
LaLaurie slowly torturing a poor black gardener to death by clipping off his toes (lots of nerve centers there) and then disembowling him. Worst of all: he was just coming inside for help because he had knicked himself outside, and no one in the house questions where their gardener went and no one comes looking for him.
Disembowling slaves for kidneys while conscious and alive.
Even worse: LaLaurie is based on a real person. Her French Quarter mansion is said to be the most haunted house in New Orleans.
The consequences of having sex with Zoe.
Madison's explicit gang rape by the frat boys. The scene is horrifically detailed, and is regarded as a horrifying scene.
It's far more intense than the Lana rape scene in Asylum, to make matters worse.
LaLaurie forces a slave to wear a dead bull's head over his face. Just think about how disgusting that would be.
LaLaurie's fate. Many would say that it was rather karmic and well-deserved, but it's still incredibly unsettling. It's a wonder she didn't go insane. That could also be chalked up to the immortality potion, which is kind of worse in a way.
"The Perfect Boyfriend" when it awakens. Evan Peters' complete rage is far scarier than anything achieved in any of the seasons so far, and it lasts only a few seconds.
While his rage doesn't last long, he seems disoriented, almost feral, and only grunts and whimpers. So far, there is no sign of the nice young man Kyle used to be.
And it gets worse in "The Replacements", the following episode. FrankenKyle kills his mother in a fit of rage to the point of caving her face in with a statue. Granted his mother was incestuous with him...
Kyle's mother is unhealthily obsessed with her son. After her son gets back home barely able to walk or speak, what does she do? She rips his shirt off, feels him up, and starts kissing him. Which implicitly triggered FrankenKyle's memories of the OTHER times she did things like that, so we really can't blame him for going nuts and bashing her face in.
Probably belongs in the Fridge, but not being able to tell the girl you love that your mother is sexually abusing you, and has been for a long time.
What Spalding does with the baby that Marie gives to him: dresses it up as his living baby doll.
Fearful Pranks Ensue has a lovely scene where a living Minotaur head is mailed to Marie's hair salon.
FrankenKyle smashing his head into the bathtub in a catatonic state, covered in blood.
Spalding took Madison's body after she was killed by Fiona and is using it as a doll. Let us hope dressing her up is the only thing he does with her...
Joan's parental discipline techniques, but especially the bleach enema. Poor Luke.
The cold steely fury on Hank's face as he shoots up Cornrow City, even killing Chantal, Marie's assistant in the process, who even surrendered in "Head". The entire scene is horrific, as it's literally in tow with the tragedies of the Civil Right Movements Delphine subjected to watch.
Though it's played for comedy, the method Myrtle uses to procure Cordelia's new eyes is still frightening, as she cuts out one eye each from Quentin and Cecily while they're paralyzed, then dismembers their bodies and dissolves them in acid.
Cordelia stabbing out her eyes with garden shears is not fun to watch.
LaLaurie and Marie's ultimate fates: Marie has to spend her afterlife torturing Bourquita, something that even she doesn't relish, and LaLaurie is forced to watch.
Hell is different for everybody, but the same in the sense that they are eternally stuck in the worst time of their lives with minor changes from their situations from when they were living. During her brief time there Queenie had a never ending work day at the restaurant she worked at before she went to the academy. The series ends with Misty stuck in Hell herself, reliving being forced to dissect a frog over and over again for the rest of eternity.
Probably is some kind of Fridge Horror but Kyle strangling Madison to death even though in the beginning of the season he was the only member of his fraternity who tried to actually stop his frat brothers when he caught them gang-raping Madison.
Don't tell me you didn't shit a brick when Marie did that white-eye-tongue-wagglin' thing and caused the two cops to fatally shoot each other. What a crazy/creepy display of power. Here's a nice reminder.
The idea of the Supreme becomes Fridge Horror when you consider the fact that you only get about 30 years of power and perfect health before a new Supreme rises and you start to slowly sicken and die
Cordelia being the Supreme at the end is Fridge Horror especially. She never wanted to be Supreme but has no choice in the matter. And not that only that... she has seen first hand what power did to her Mother. To be not only the Supreme but a better Supreme than Fiona will require great personal sacrifice... not the least of which is to die in order to make way for the next Supreme. When Cordelia watches her Mother die she is getting a grim look into her own future
And what if she does manage to have a daughter of her own? Cordelia's eyes were healed when became the Supreme. It's quite possible her fertility issues were healed as well. Or that they could have been caused in the first place by her actively repressing her powers. Considering that Cordelia herself becoming Supreme shows that the power can be passed down from mother to daughter and that any child she had would come from 2 generations of Supremes... its very likely any daughter she had would be the next Supreme after her. So Cordelia would know her child would have to watch her sicken and die and that the child would one day suffer the same fate
Fridge Horror occurred to this Troper when watching 'The Replacements.' Fiona says it's a dance she's known since she first saw her reflection in her Father's eyes. Since she's very clearly talking about sex... this line becomes creepy as hell if you think about it for a moment. Is she implying that he had sexual thoughts about her that she was aware of due to her powers? Or something even worse?