This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Sons of Anarchy
Abel's kidnapping at the end of season 2 and Jax not arriving in time to stop it and instead sees them leaving with his child, helpless to do anything. Easily something any parent would wake in a cold sweat over.
An expelled ex-SAMCRO member returns to Charming, where it is revealed that he had not undergone the process of having his SAMCRO reaper back tattoo altered to cover up the gang's name. Needless to say, this does not set well with the members of the gang, who give him the option of having the tattoo burnt off with a welding torch or having all of the flesh from his back sliced off. He chooses the former, leading to a graphic scene where he (willfully) is strung up by chains and has his back horrifically burnt in order to remove the tattoo. Real biker gangs have been known to do this to the gang tattoos of exiled members or other people who claim a false association with the club.
Jax beating the crap out of a meth dealer culminating in his jamming a pool cue into his crotch and leaving it standing out of his prone body like a flagpole.
Tig has to watch as Pope douses Tig's daughter in gasoline and burns her alive.
Real-life example: Johnny Lewis, who played Half-Sack, allegedly beat his landlady to death (and dismembered her cat), then, in a bizarre turn of events, fell from a roof while making his escape and died. Drug tests were negative, but people have come forwards to claim he had become mentally unstable. Brr.
If you thought it wasn't possible to surpass the disturbing level of Gemma's rape in the season 2 premier, Kurt Sutter blows right past it in the season 6 premier when we see Otto getting raped in Stockton at the behest of Toric. The worst part? It's been happening every morning since Otto bit off his own tongue, and will continue until the state executes him. At this point, execution would be an act of mercy.
Bear in mind that Otto is blind and minus a tongue. So while all this is happening to him, he can't even see whats going on. And he can't even talk to anyone about whats being done to him. I think its safe to say that Potter was right on the money when he said that Otto has endured the most suffering for his club than anyone we've ever seen.
Otto doesn't wait until his execution, instead killing Toric (the architect of his suffering, who in turn was retaliating for Otto murdering his sister, the nurse) and then taking his own life.
Lyla begging for Opie after being tortured on film for some dirty porn producers. Clearly she's terrified, and we're all reminded one truth. Opie is gone.
The big wham at the end of the season 6 premier. If you have a kid, or even a nephew like this troper, this definitely touched on your Adult Fear. All I'll say is it involves a kid, a book of disturbing drawing, self inflicted wounds, a school, and a KG-9.
Alice Noon and her being a child porn queen. The studio is more detailed than most would feel comfortable about.
Tara's death. Plenty of squick, considering she had her head dunked in a sink full of dirty dish water, and was then repeatedly stabbed in the back of the head with a carving fork. Definitely one of the more brutal deaths in the series, even more so when you realize it only happened because Gemma was drunk and thought Tara had turned Jax in. In reality, Jax had decided to turn himself in, so Tara was brutally murdered over a misunderstanding.
The scene where Bobby gets his eye cut out by August's men. Yes, there is a Gory Discretion Shot involved, but the sounds alone make it difficult to watch. Even Tig was disturbed by it.
He had it coming, but Moses' death. His eye's gouged out by Jax's bare fingers, he has a few fingers cut off, and then he gets shot in the head. But unlike Bobby's torture and death, everything is shown onscreen.