* Not even counting the shipwreck, Oliver's castaway ordeal was nightmarish before he ever reached the island. Namely on the life raft, Oliver watching his father murder another man and then [[BoomHeadshot kill himself]]. Oliver spends countless days floating aimlessly a few feet from his father's ''sun-bloated, near-headless corpse'' as the water slowly runs out. He finally reaches the safety of the island's dry land, only to watch seagulls feasting on his father's rotting body. Even if Oliver had been rescued the day after he reached the island, he already experienced enough horror to justify spending the rest of his life gibbering in a padded cell.
* The effects of Vertigo when put in the jugular. It puts the brain's pain receptors on overdrive, causing a crippling amount of psychosomatic pain that can last for ''days'' before the person's heart gives out.
* The Undertaking: A bunch of rich, powerful people decide to "fix" their city by making the poor side of town the worst it can be, probably to justify whatever renovation efforts they care to make. In the process they do things like corrupt the legal system, stop gentrification projects and shut down free clinics and other social support organizations. If you're one of the poor people harmed by this project, oh well...
** Turns out they were actually trying to save the city, but the Undertaking is now bringing down the Glades with bombs to make it look like a freak earthquake destroyed them!
** Malcolm's SuddenlyShouting moment right before the Undertaking takes place, which somehow crosses this with TearJerker. It's both completely tragic and shows how completely crazy he's become since his wife's death.
* Deadshot. Even if you survive with just a graze, you'll be dead from the curare poison he laces his bullets. And good luck using bulletproof glass. He'll just shatter it and fire another round immediately after.
* The Island as a whole. With UsefulNotes/WW2 mines laying about, armed mercs who'll grab and attack anyone they see and torture for info they may not even have, the fact that both a crashed plane and two boats have ended up there like the Bemuda Triangle, and the questionable implication of what, exactly, the hell are they even doing there. The realization that it was able to transform a shallow party boy into a hardened killer in mere years will make you think twice about any trip over seas.
* The Doll Maker. The first victim we see of him is treated in a more gruesome, CSI kind of way and when Quentin sees the body, he's visibly disturbed. The killer himself is creepy as hell, and takes disturbing pleasure in drowning his victims and turning them into his dolls.
** "Broken Dolls" also gives us [[spoiler: Slade getting hit by one of the pirates' mortars and set on fire. It is later shown that the damage caused an extremely nasty burn on the entire right side of his head.]]
* In "Crucible" [[spoiler:Sara Lance says, "No woman should ever suffer at the hands of men." Some fans have pointed out that this may be an oblique reference to being raped at some point during the six years she was missing. At any rate having spent the time on Amazo, Lian Yu, or in the League of Assassins she's likely to have been through some terrible things - equal to or greater than Oliver.]]
** ''League of Assassins'' has her, when she's first found by the Amazo, being dragged out in front of several men in nothing but a shirt and her underwear, with the obvious implication they were planning to gang-rape her. Dr Ivo saves her from it, but she's left terrified and shaken, so much so she flinches when he locks the door (not to stop her leaving, mind, to stop the others coming in).
* Speaking of such, the League of Assassins themselves; highly trained assassins capable of catching arrows without flinching, almost immune to pain. Their ranks are large and they can come in, take out their target, then leave without ever being seen, with only rumours of their existence in the far east, despite them operating throughout the world. They transform people with no combat skill prior into ruthlessly efficient killers, in less than two years time. And given that the show is now embracing super powers, its possible Ra's Al Ghul may in fact keep his immortality here, making him all the more scary.
* "The Scientist" confirms that yes, [[spoiler: Professor Zoom does exist in this universe, and he's already jumping around Barry Allen's timeline.]]
* From "Three Ghosts" Oliver's hallucination of Slade attacking him, especially when we learn [[spoiler:the hallucinations are purely psychological.]] He gets beat up, tables are tossed, and thrown into a glass case, and all the time we know that he's doing it to himself.
** Plus, this scene is highly reminiscent of Robin's hallucination of Slade [[spoiler: (also thought to be dead)]] in ''[[WesternAnimation/TeenTitans Teen Titans]]'', and it was mighty effective then as well.
* [[CurbStompBattle Cyrus Gold's fight against the police.]] It has a very creepy, horror movie feel as the panicked cops shine their lights around, trying to find Gold.
** Cyrus Gold's [[spoiler:death]] bordered on BodyHorror.
* The Count. He was creepy enough to begin with, but once the Vertigo takes affect, he's left completely insane and terrifying on a whole other level. Even worse, he's played by [[{{Series/Fringe}} Lincoln!]]
* What happened to Sebastian Blood's parents: [[spoiler: he killed his father and framed his mother for it, putting her in a nuthouse. When Laurel sees his mother, she seems to be in a MadnessMantra. When Laurel mentions Sebastian's name, it snaps her out. You know something's messed up when your own mother calls you the Devil.]]
* In "Blind Spot", the mind games that Blood plays with the already fragile Laurel are terrifying, to the point that she can no longer trust herself.
* From "Tremors", the effect that Mirakuru has on its victims. Roy goes to see Thea and begs her to leave the city. She asks for a reason, and within ten seconds he gets frustrated and starts unconsciously ''crushing her arm''. He realizes what he's doing and stops before she's hurt, but it's still very disturbing both to [[MyGodWhatHaveIDone Roy]] and the audience. In the flashbacks, Slade nearly blows up their only way off the island in his desperate mission to avenge Shado, and almost kills Ollie.
* William Tockman, the Clock King, in "Time of Death". A meticulous planner and creepy master thief who, regardless of his ostensibly noble motivation, will stop at nothing to get what he's after, and even [[spoiler: hacks the Foundry's computers and makes them blow up while Felicity and Diggle are still inside]]. Talk about ParanoiaFuel.
* In "The Promise", we have [[spoiler: Slade on Mirakuru learning the full story of Shado's death and undergoing his inevitable FaceHeelTurn. Even before then, he dishes out a MookHorrorShow while wearing the Deathstroke mask, and after his turn, he chases down and catches Oliver, imprisons him on the ship, [[AsskickingEqualsAuthority kills the Captain and takes over]], and ''[[AnArmAndALeg chops off Ivo's hand]]''. He has become all but unstoppable, and his rage is chilling to witness]]. Oh, and the ''very last shot'' is of [[EyeScream Slade with his eyepatch off]].
* The ending of "Birds of Prey" is pure AdultFear. [[spoiler:Thea goes out alone at night and [[BigBad Slade]] drives up to offer a ride.]] And for more [[PsychoSerum Mirakuru]]-related goodness, we have Roy crushing the shoulder of a guy who bumped him and refused to apologize. Listen closely enough and you can hear [[SickeningCrunch crunching]].
* "Deathstroke": Back on the island, [[spoiler: Slade hallucinating Shado when he has Oliver and Sara at gunpoint. Given the role she played as a MoralityChain in past, you might expect her to be the conscience. Nope, she's advising Slade to keep them trapped on the island and go after their families. What's worse? He's still seeing her in the present day]].
** Same episode: [[spoiler: How did Slade get off the island? He swam until he reached land. Not so bad? He got pulled under by the current and crushed against the rocks, which apparently cut his flesh to the bone. He survived and healed thanks to the Mirakuru, but ''Jesus'' that sounds painful.]]
*** [[spoiler: Adding to this, Slade had one eye exposed to saltwater, thus making what happened to him more horrendous.]]
* "The Man Under The Hood": [[spoiler: Isabel gets Mirakuru. Slade was a heroic, well-meaning person before he got injected, and it made him a dangerous psychopath, but Isabel was pretty much a sociopath before her dosage. Who knows what this is going to do to her.]]
** [[spoiler: Slade's surprise attack on Team Arrow, where he's just waiting for them in the lair and completely wipes the floor with them, makes a pretty effective JumpScare.]]
* "Seeing Red":
** [[spoiler: Roy, completely hopped up on Mirakuru and reduced to a near-mindless state, going on a violent rampage and curbstomping everyone who's unlucky enough to come across him, often involving him breaking their limbs and the violent, stomach-churning snaps that go with them. One cop isn't even that lucky, as Roy proceeds to violently shove one of Oliver's arrows right through his gut.]]
** [[spoiler: His hallucination of Thea, who begs him to kill her.]]
** [[spoiler: This one crosses over with TearJerker: Slade's SadisticChoice and murder of Moira right in front of Ollie, while he's tied up and helpless to do anything about it and his sister is sobbing and crying the whole time.]]
*** [[spoiler: Equally terrifying is the InternalReveal from [[TheCorruptible Slade]] to [[TheAtoner Oliver]] that he's hallucinating Shado. He screams that "she" told him [[BelievingTheirOwnLies the "truth" of what happened with Shado and Sara]], not even realizing that [[{{Hallucinations}} nobody's there to talk to him]]. It's clear that as much as Slade wears a FauxAffablyEvil WickedCultured persona now, his MaskOfSanity is slipping ''fast''.]]
*** [[spoiler: Which extends into his murder of Moira. If the narrative was from his perspective, then we would see his remorse and hesitation challenged by the hallucination of Shado, who ''insists'' Moira be killed. Slade acknowledges Moira's courage, but Not-Shado insists she be killed because sparing her wouldn't teach Oliver anything. Notice how his acknowledging her courage is spoken with a wavering voice, with a look of regret. Now compare that to his tone and expression right before he drives his katana into her heart. He succumbs to Not-Shado, to his darkness, and forces himself to kill Moira for the sake of his mission. But once she's dead, once he see what he's done, his energy is spent, which shows when he frees Thea. He's completely devoid of any emotion, and just leaves.]]
*** [[spoiler: On Oliver's end, we see him completely break. The promo for the next episode shows he's disappeared on everyone again, just like at the beginning of the season when he went back to the island to grieve for Tommy's death. Unlike Robert's death or Shado's death, where Oliver was forced into a situation he had no control over and therefore had to trudge along to keep surviving, this is a situation he saw coming. It was something he was fully aware of and should have been able to prevent. But once Moira hit the ground and he looked into her dead eyes, he lost it. He was back on the island again. But this time, he'd lost the family he had left behind. To him, there's no hope left. To him, there's no reason for anything.]]
* "City of Blood": Ivo's last "gift" to the world was to [[spoiler: purposely give the friendly Peter cancer in order to see if Mirakuru could cure it. With no treatment, the cancer has grown into an easily visible and unsettling-looking infection that's slowly killing him]]. This makes his own infection retroactive LaserGuidedKarma.
* "Streets of Fire": [[spoiler: Let's start with the basic horror that a bunch of borderline unstoppable thugs are tearing through the city with the explicit orders to tear as much of it down as possible, and kill as many people as they can.]]
** [[spoiler: The brown skull mask that Brother Blood wears is a representation of [[AbusiveParents how he saw his father]].]]
** Especially scary is the fact that, until now, [[spoiler: each person who received Mirakuru at least had some kind of goal or order to their actions. Slade is an assassin with a specific plan who seems to have trained himself to control his explosive temper to the point he doesn't just go straight to killing Oliver; Cyrus Gold was operating under specific orders on what to do and carried them out; and Roy is instead a hero in training. These soldiers, however, were just random criminals; they could be drug addicts, petty thieves, or money launderers, but they could also be killers, rapists, psychopaths and sadists, any such brand of evil, and now there's nothing to stop them doing what they can, and while they have their orders, they're unspecific enough to let these people do whatever they want. And there's nothing to stop them attacking anyone they see, or going anywhere they want]].
* The fate of [[spoiler: Deathstroke. Locked away in a secret military prison, presumably without a trial. The Nightmare Fuel comes from that fact this isn't Hollywood ignoring the law/due process/etc, for the sake of storytelling. It's ''perfectly legal'' in America for anyone suspected of terrorism (and Slade was absolutely a terrorist, even though he only wanted to "terrorize" one person in particular, he was willing to kill ''thousands'' to make his point) to be detained indefinitely without a trial.]]
* Laurel going completely Huntress in the wake of [[spoiler:Sara's death]], including slamming the injured arm of another of her target's victims against the rail of his hospital bed.
* One of the files Felicity recovered for Ray Palmer was entitled [[spoiler:O.M.A.C Project]]
* Roy's nightmare at the end of "The Secret Origin of Felicity Smoak". [[spoiler: He sees that it was him who killed Sara, and given what she said in the dream being exactly what she said when she died (something only the killer would know), would mean that the dream is accurate, and he ''is'' the killer, though given the fact he appeared possessed and demonstrated enough strength to ''throw arrows like darts'', implying that he still has Mirakuru-level strength, and has developed some kind of SuperpoweredEvilSide. But, the really disturbing part? Given his comments about not having much sleep recently, it could mean that ''this isn't the only time this side has came out''.]]
** [[spoiler: Except he's ''not'' under its influence and he ''didn't'' kill Sara -- the very next episode, "Guilty", reveals at the end that Sara's death by arrows triggered his subconscious to push forth the repressed memory of him killing the cop in "Seeing Red". Still frightening, and the InternalReveal leaves him devastated, but there's no SuperpoweredEvilSide left.]]
* Oliver's duel with Ra's al-Ghul in ''[[Recap/ArrowS3E9TheClimb The Climb]]'' shows just how dangerous a threat the latter is. [[spoiler:Oliver has been established as a highly skilled combatant, but even though he's apparently among the best Ra's has fought the Demon's Head still delivers a CurbStompBattle that's ''very'' brutal (all while remaining perfectly calm and in control), ending in Ollie's ''apparent death by being impaled and thrown off a cliff''. This isn't even an enemy pumped full of supersoldier drug like Deathstroke was]].
* Murmur is quite an unnerving villain, with the mouth sewn shut, the creepily efficient way his gang operate and his ultimate plan: [[spoiler:steal cheap industrial diamonds and use them to make diamond-tipped bullets. He then attacks the police precinct, killing several cops]].
* Deadshot's backstory, where he suffers a horrific bout of PTSD that ends with him pointing a gun at his wife. It's an unnervingly realistic plotline in this comic book show.
* Thea [[spoiler: getting drugged in order to kill Sara]] can be akin to/tied as a metaphor for rape. Malcolm drugged and used his daughters own body for his doing, and that's something that Rape survivors can relate too. And the scariest and most realistic part? Most people (even some of the writers) are defending him instead of Thea.
** Thea and Malcolm's relationship is a spot on case of EXTREME child abuse. Manipulating your daughter into trusting you multiple times even though they know you're a disgusting person? Check. Killing your son and mentally raping your daughter? Check. Turning your daughter into a human weapon to wipe a blood debt while violating her body with a mind control drug? Fucking. Check.
** And the fact that Thea is constantly handed back to Malcolm, HER ABUSER makes it all the more terrifying.
** Thea was only 19 years old when she was drugged to [[spoiler: to kill Sara]]. Who drugged her? Malcolm Merlyn, a ''55 year old man.''
** Also doubles as a tearjerker, Thea only wanted to learn how to defend herself and even protect others. She could've gotten that, but she ended up being used and becoming a meat shield for her ''only parental figure left in her life.''
*** The worst part? Not only does Oliver let Malcolm slide for this, he gives Malcolm control of the league. Just think about the damage Malcolm can do now!
* The way that [[spoiler: Sara dies- it's terrifying, if you think about it. Shot three times in the stomach and landing back first onto the edge of a dumpster, breaking your back if there's enough force and speed from the fall, and having 3 holes in your stomach]] And guess what? the arrow's wouldn't have killed her, ''the fall did.''
* [[spoiler: Ra's murdering Thea. He appears in her apartment out of nowhere, appears to teleport in front of her when she tries to escape, and then Curbstomps her with out effort before finishing it by stabbing her with his sword. Not only is it like something right out of a horror movie, but he's just so cold and efficient about it.]]
* Nyssa [[spoiler: being forced into a heterosexual marriage]] is nightmaric for rather realistic reasons: A LOT of queer people are forced to be straight to protect themselves, and Nyssa being rather open (though not calling herself queer) about her sexuality has had a rather big consequence towards her status as an heir and causes her to be disowned (along with her being a woman)
* A meta example, Ra's [[spoiler: wanting Nyssa to produce an heir for him]] sounds a bit like rape. One of his lines is "You will have no say in this like how your mother didn't," possibly stating that Ra's may have raped Nyssa's mother to produce an heir. As well, it does seem that if Nyssa was to produce another female heir, Ra's would have that heir raped as well for his male heir, which shows off that while Ra's may be polite to a fault with most people, get on his bad side and he will ''never'' forget.
** The line also points out that Ra's is expecting and willing for Oliver to rape Nyssa for an heir.
* In "My Name Is Oliver Queen", the flashbacks show the aftermath of an absolutely horrific bout of ColdBloodedTorture instigated by [[spoiler:Oliver]] on [[spoiler:Shrieve]]. [[BrokenBird Tatsu]] shows horror at this.