Deangelo wandering back in to the office after having been hospitalized with a head injury, attempting to give out orders despite aphasia making him into a disturbing version of The Unintelligible.
Dwight's "fire drill," while hilarious, is also horrifying. The panic of all the office workers goes on for a four minute long cold open, with things like Michael smashing open a window and screaming pretty un-hammily for help, Jim saying, "I am not dying here!" Dwight's Dissonant Serenity, oh, and Stanley having a heart attack. It's pretty unnerving.
Also in the same episode, when Dwight cuts the face off the CPR dummy and wears it as a mask.
To top it off, the lead-in was Super Bowl 43.
Someone made a particularly disturbing edit of the scene which removes all of the comedic moments and adds tense music to the clip, heightening the unnerving tone of the scene even more (and making Dwight look even MORE like a psychopath).
To emphasize how serious the situation was and how badly Dwight messed up, David Wallace calls out Dwight for his stupidity and Michael for wanting to simply give Dwight a warning. He points out that Dwight caused immense property damage and Stanley almost died. Michael admits David has a point.
Roy going berserk (in a not even remotely comedic way) in "Cocktails" and "The Negotiation".
"I'm going to kill Jim Halpert."
The next episode opens with him pacing outside the office in a disturbing fashion, before finally deciding to enter the building, shout "HALPERT!" in a vengeful tone, and make at go to assault Jim right there in the office, before Dwight subdues him.
Sprinkles' fate in "Fun Run." It's bad enough that Dwight force-fed her pills and put her in the freezer, then she barfed them up and tried to claw her way out, according to Angela. Poor Sprinkles.
"Yeah, it seems like there isn't a narrative. Maybe the filmmaker realized that even narrative is comforting.
Pam almost getting beaten up by a surly warehouse worker. Luckily, it was prevented, but he got really close...
"You don't even know my real name. I'm the ''(bleep)''ing Lizard King!" If you didn't think Robert California was sinister before, this line would definitely do the trick.
"Dinner Party" counts as this. In what could be best described as the show's answer to Who's Afraid of Virginia Woolf? Jim, Pam, Andy, Angela, Dwight and Dwight's Babysitter-turned-lover are essentially Forced to Watch Michael and Jan's relationship fall apart at the seams. Doubly effective if you've ever had to witness a similar situation among friends or loved ones. Triply when you consider what must be happening when they're not on camera or around people. We see Jan smash Michael's TV, and they both talk about Michael running through the patio door while chasing the ice cream man.
The face Michael makes when Pam realizes he's dating her mother. Seriously, he looks deranged.
Michael pretending to hang himself in the haunted house in "Koi Pond". There's a reason the scene was pulled from future airings and DVD releases.
According to Dwight, the secret to making horse meat is cutting bits off the horse one at a time.
From "The Merger":
Dwight: "Japanese camp guards of World War II always chose one man to kill whenever a new batch of prisoners arrived. I always wondered how they chose the man who was to die. (Beat) I think I would have been good at choosing the person." (A Slasher Smile begins to creep across his face)
"Weight Loss: Parts 1 & 2" has a talking head of Kelly stating she bought a tapeworm from Creed in order to lose weight with the intention of using tapeworm-medicine to remove it. It cuts to Creed bluntly stating "That wasn't a tapeworm".
Dwight has wigs allowing him to impersonate many Dunder Mifflin employees. This is played for laughs at first, but as Jim actually falls for it, the viewer realizes that Dwight has a means of passing as the friend or loved one of any number of people. Not indefinitely of course, but just long enough for it to matter...
For those who are afraid of vomiting, the cold open to Niagara: Part 1 is this big time.
Dwight dangling from a tightrope after his attempt to bicycling across it failed when the printer counterbalance was too light is this. It's a miracle he was able to hold on to the handlebars long enough for the fire department to arrive. If he hadn't, he likely would have died or at the very least been seriously injured
Nellie adopting a child. It's easy to forget during Season 9 how incredibly naive, unstable and manipulative she is, but looking back at Season 7 or 8, one cannot but cringe at the idea that a child would be left in her care.
Not to mention she only got that baby because Ryan decided to abandon his infant son and run off with Kelly.
It's possibly worse than that. We have only Ryan's word that this is even his child to begin with, and he's enough of a sociopath that "single father" actually feels less likely than "kidnapped a baby just to distract his ex-girlfriend's husband."
To top it off, she declares to the cameras that if Ryan wants his baby back, he can find them "somewhere in Europe".
The final scene in "Classy Christmas". Dwight has made Jim paranoid and in fear over his snowball pranks. In this scene, Pam and Jim walk out and see a crowd of snowmen with large black holes for their eyes and mouths. They both then walk through the crowd as Jim anxiously looks around in a completely silent scene. Jim, in one of the few moments of fear he's had, beats on every snowman around him as Dwight looks on from the roof.
Dwight: "In the end, the greatest snowball isn't a snowball at all. It's fear. (smiles) Merry Christmas."
For all his hilarity, Dwight may be one prank away from going postal and showing up to work with an AR-15. He's typically portrayed as an ill adjusted loner with violent power fantasies who is regularly bullied by certain coworkers, ignored and belittled by his superiors, seems to enjoying killing peoples pets and generally regarded as 'crazy'. He already brings weapons to work and is shown to be more than willing to use them on his colleagues such as pepper spraying Roy and Andy and tranquilising Stanley.
Season 3: The Coup. Michael tricks Dwight into believing his attempt at usurping his position worked. We see Michael suddenly become cold, calculating and decidedly not his usual self. The jarring effect can make it quite scary that even though the humorous way he ends up telling Dwight he knows what he did (Dwight insults his car), is lessened by Michael reducing the man to a quivering wreck on his office floor. Michael does not like being betrayed.
In a deleted scene in New Leads, when Jim tries to convince the rest of sales to make peace with the rest of the branch, Stanley recalls how his beverages tasted coppery when he treated his wife poorly, but faded away when he dropped such a behavior. The rest of the sales team become horrified, with Andy nervously asking Stanley to clarify if he does suspect his wife tried to poison him and Jim making a terrified glance at the camera whispering oh my god. Makes you wonder...
of the scene which removes all of the comedic moments and adds tense music to the clip, heightening the unnerving tone of the scene even more (and making Dwight look even MORE like a psychopath).