Jenna's transformation into a vampire from her and others' point of view, especially her roommates. Jenna thinks she is merely sick. Her roommate comes across her corpse and is visibly distressed. As she is being wheeled away by paramedics, under a sheet, she suddenly sits up and scares the shit out of the paramedics. This drives Jenna's roommate to become a vampire hunter.
The scene where the main characters are being burned alive by the sun is terrifying.
The teleportation of the vampire children in "The Curse". Not only is the effect itself eerie, the camera is focused on Guillermo finally convincing Shanice that they've broken into a normal human house—so it takes a second for the viewer to realize that he's very wrong.
Simon's new follower Carol looks like a shriveled, subhuman cave creature, has bulging white eyes, acts feral, and speaks in an otherworldly hiss.
Season 3 introduces the Sire, the oldest and most savage of all vampires, unseen behind a chained door and only heard by his monstrous roaring... until he escapes.
Cult leader Jan. As hilarious as it is to watch Cree SummerChewing the Scenery in a rare live-action role, the fact remains that she's dangerously charismatic to the point of convincing an entire commune of vampires to walk into open sunlight—to their deaths—by making them believe they were on a path towards becoming human again. It's not unlike how real-life cult leaders have operated.
Jan's monologue as they're walking out into the sun bears a disturbing resemblance to the Jonestown tape.
Laszlo suddenly shoving the human Guillermo into a shipping coffin and closing the lid is terrifying, mitigated only slightly by the reveal he put "a hole" in it somewhere, and only made worse by Guillermo's panicked screaming.
The hybrid animals made from Guillermo's blood are rather creepy looking.
Collin Robinson is kidnapped by a council of energy vampires and their conducting of a meeting is tortuous to him and they are feeding on him at the same time.
The Baron becomes this in Season 5 after he learns that Guillermo was the one to burn him up and that he has vampire hunter heritage. The Baron takes the stage to call out the other assembled vampires for growing soft and weak over the years, before angrily chasing down Guillermo to kill him. Notably Guillermo, who's shown that he can kill lesser vampires with ease and fought Nandor to a standstill, is scared enough that the only thing he can do is run.
Eventually Nandor learns the truth, which he considers especially dishonorable since he was the very last person to discover that his familiar was turned by another vampire. Nandor flies into a murderous rage so intense he's able to grab pure silver in his hands and not wince at the pain. Guillermo understandably goes on the lam. The otherwise apathetic housemates are also disturbed at Nandor's bloodlust and track down Guillermo so they can express their concern for his wellbeing. Nandor even goes so far as to call Guillermo from his mother's home, revealing he's been there for some time and calmly threatens her life to force Guillermo to show up.
Guillermo finally becomes a full-fledged vampire after ingesting human blood. The sensation immediately drives him into a bloodlust and he demands to go out on the town to hunt innocent people. It's only when he witnesses the other vampires feeding on a restaurant full of corpses that Guillermo realizes what he's become and is disturbed by what he assumes will be the rest of his life.
