* Not even counting the shipwreck, Oliver's castaway ordeal was nightmarish before he ever reached the island. Namely [[spoiler:on the life raft, Oliver watching his father murder another man and then [[BoomHeadshot kill himself]]]]. Oliver spends countless days floating aimlessly [[spoiler: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 [[spoiler: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!
* Deadshot. Even if you survive with just a graze, you'll be dead from the curare poison he laces his bullets. [[spoiler: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 also 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.]]
* "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 as lucky as that though as Roy proceeds to violently shove one of Oliver's arrows right through his gut.]]
** [[spoiler:His hallucination of Thea, who tells him to kill her.]]
** [[spoiler: Slade's SadisticChoice and murder of Moria 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.]]

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