- In "Fusion," we get one of the emotional Vulcans, Tolaris, and his Mind Meld with T'Pol, that quickly turns into a Mind Rape. She very plainly tells him to stop, and he refuses. It's viscerally unpleasant to watch.
- "Shockwave part 2". T'Pol undergoes Cold-Blooded Torture at the hands of Silik. Seeing the normally-composed Vulcan shivering and barely coherent is troubling.T'Pol: ...the science Vulcan directorate has determined that time travel is...not fair.
- The Xindi-Insectoids are enormous computer-animated ants. Industrial Light and Magic gives us all the detail on them you'll ever want and then some.
- The automated repair station in "Dead Stop" that turned out to kidnap crewmembers and fake their deaths so it could use their brains in its computers. Archer blows it up in the end...but the final scene shows it beginning to put itself back together.
- Worst of all, though, is the much more graphic portrayal of what happens to victims of Explosive Instrumentation. When the NX-01 gets attacked, other Trek shows and movies have the Star Trek Shake and the occasional sooty He's Dead, Jim person; Enterprise has things like people on fire and screaming, or crewmen blown out into space when the hull is breached, twitching for a bit, and then stopping.
- The specific examples mentioned just above are shown in "Azati Prime," perfectly demonstrating just how bleak things have become for our heroes in their search for the Xindi superweapon.
- Most of "Strange New World" is creepy, but the worst is when they beam up Crewman Novakovich during a storm and he materializes with sticks and debris embedded in his face and body.
- The aliens/Elachi in "Silent Enemy". They come out of nowhere, say nothing and are extremely unpredictable in how they act. They're also shown to be capable of effortlessly crippling and toying with the Enterprise. When they actually board the Enterprise, we get to see them... And you'll wish you hadn't. One shudders to think what would've happened if they had managed to capture the Enterprise crew...Expanded Universe
- "Singularity" seems like a "Naked Time"-ish episode, where everyone is obsessed with tiny tasks and becomes extremely agitated. T'Pol is unaffected, so she goes to check if Phlox is also all right. He isn't. He has become so obsessed with Mayweather's headache that he's going to vivisect his brain, seeming identical to the Mirror Universe Phlox, and threatens to kill T'Pol for getting in the way of his experiments.
- In "Doctor's Orders," Phlox experiences hallucinations whilst he and T'Pol are the only members of the crew awake for a trip through radiation that is dangerous to humans. At the end, it's revealed that Phlox was hallucinating T'Pol as well. She was really sleeping along with the rest of the crew.
- The above two examples, Phlox's decision to support what is essentially genocide-by-inaction in "Dear Doctor" and his Mirror Universe counterpart being one of the least radically different in terms of personality, has lead more than one viewer to suggest that Phlox is actually a dangerous nut seconds away from cracking and going on a killing spree!
- "In a Mirror, Darkly" takes the agony booth and shows what prolonged exposure can do to a person. Mirror!Archer is apparently insane after ten hours in Mirror!Reed's invention; it's just that the culture of that particular universe is so toxic nobody can tell, and even if anyone can tell, they dare not say so aloud; with Forrest dead, he's now captain.
- "Exile." Think Serial Killer drama combined with Beauty and the Beast. First, Tarquin tries to entice Hoshi with a form he thinks will be attractive to her...while whispering in her skull, making her hallucinate him on all the viewscreens in the command center, and generally causing her to think that she's losing her mind. (Again.) When he does make contact, he makes her stay in his house in exchange for his help and demonstrates that he's been rifling through her memories to the smallest detail (never once asking her permission to do this, even her more painful memories) and tries using them to convince her to stay. When that fails and she finds the graves of his previous "companions," he creates an illusion of Archer essentially ordering her to stay and then attacks Enterprise itself. She has to threaten to break his telepathy amplifier to make him let her go. Freudian Excuse or not, that is some major-league creepiness.
- "Regeneration" presents a trio of Borg that are less formidable than in previous appearances, yet manages the feat of making them considerably scarier than they had been in quite some time. They almost reach a kind of Villainous Valor as they attempt to make their escape, infecting anyone they can with nanoprobes (whose effect on Phlox is Nightmare Fuel all by itself) and cleverly disrupting Enterprise's systems in order to buy enough time for them to modify their obviously-inferior ship enough to pose a threat.
- What really makes the episode work is following the scientists for the first act as they investigate the Borg debris. It plays entirely like a horror movie, where the audience knows that the monster is coming and the characters are completely unaware. When one of them remarks that the unknown aliens could be entirely friendly with earnestness, the audience knows better, and every second something doesn't happen ramps up the tension for when it finally does.
- "Cold Station 12" shows a man being subjected to Cold-Blooded Torture via Symbalene blood burn. Between the Blood from Every Orifice and the agonized pleading for release, even Dr. Soong (who is allowing it to happen) is disturbed by his suffering.
- Trip's and Hoshi's faces when they are sick in "Observer Effect" is Nightmare Fuel. So was the possibility of them dying, and the non-physical aliens, but the biggest scare provider was Hoshi of all people. She was delusional, made speaking in foreign languages seem scary, threw up at one point, making it worse because Trip was also sick but he didn't throw up, and once mentioned that she broke somebody's arm.
- "Impulse" has a crew of Vulcans who have all gone insane, and T'Pol isn't getting much better, getting more and more unhinged throughout the episode and even pulling a phase pistol on Archer. They manage to get her back to Enterprise and she's expected to make a full recovery, but she sees the dead Vulcans on the ship. One attacks her in the turbolift. And then she wakes up and ONE IS STANDING RIGHT OVER HER before she wakes up again. That last minute does a good job of making it clear that she'll recover, but it won't be a fun couple of days. Making it worse is the fact she never fully recovers, as her ensuing trillium addiction demonstrates.
Nightmare Fuel / Star Trek: Enterprise