- Electro. He went from a bullied college student and self-described "human pinata" Max Dillon to a ghastly electrical wraith-like Humanoid Abomination. He's constantly coursing with electricity, resembles a horrific ghost more than a superhuman criminal, and is downright emotionally disturbed due to being bullied all his life. Add to the fact, he's more than willing to electrocute those who've wronged him in full detail. In his first appearance, he blatantly tortured and murdered the college fraternity brother who'd been bullying him throughout the episode at a frat party via electrocution and would have done the same to everyone else present if not for Spider-Man plugging him into the landlines and trapping him in the city's electrical system, which actually made things much worse!
- The next time he appeared he was driven even crazier by loneliness and tried to make another "Electro" like himself by turning the last person he ever connected with, Sally Johnson, into one against her will. At least not before testing the process on other people like his former chemistry professor, nearly killing her. He then went about stalking Sally through her electronic devices, fully exploiting the Paranoia Fuel aspects of his powers and nearly driving Sally insane with fear. Not to mention the part where he tried to touch Sally by manifesting himself out of her television. It really says something that Spidey chose to outright violate his normal Thou Shalt Not Kill rule the first chance he got when he managed to trap Electro and toss him into the harbor. He was truly that dangerous!
- The Gaines Twins are Nightmare Fuel in spades. They're a telepathic pair of creepy twins with a penchant for using their powers for Mind Rape and Mind Control. The first chance they got free of imprisonment they had a prison guard blow another prison guard's head off with a shotgun for telling how they got moved to a new prison.Prison Guard: Guards, plural. Three of 'em. The Twins took control of the weakest. Made him turn on the closest one. He worked him over till he bled to death. The third just curled up into a ball and started crying.
Kraven: My old friend, the Amazing Spider-Man. What a nice surprise.Spidey: I'M GONNA RIP YOU APART, KRAVEN![...]Kraven: I'm not going back to the gulag!Spidey: Don't worry. I've got other plans.
- The twins tried to use Spidey to kill Kraven because he was responsible for their parents' deaths and nearly succeeded if not for Spidey realizing a flaw in their illusion at the last minute. They also managed to nearly make Spidey kill one of his closest friends and ended up having her put in an irreversible coma and basically made him quit altogether.
- Worse is how they didn't need to overtly control Spidey to make him want to kill. They just made it seem Kraven had killed Mary Jane and the rest was Spidey's own volition. Saying he was terrifying during his Roaring Rampage of Revenge is an understatement.
- The particularly nasty way that Spidey tried to kill Kraven. He tried to hang Kraven from his neck like a noose from the rafters using his webbing until he slowly suffocated to death while Spidey could watch the whole thing. When Spidey stops being nice he turns into a sadist!
- It's been well-established that if Spider-Man isn't engaging in witty banter during combat, you likely won't be walking away. But this incarnation of Spidey... the amount of malice in his voice is deeply unsettling.
- Shikata decapitating her benefactor in "The Sword of Shikata", which is especially unnerving because of the Gory Discretion Shot provided by focusing the camera on the animal heads mounted on the walls.
- The Lizard/Curt Connors tearing apart the criminal that had accosted Curt earlier by breaking into a police station. All that left was a disembodied hand and a head. Worse is that due this version of Curt Connors being a Jerkass, it doesn't take long for the Lizard to truly take over and basically kill anyone that pisses Curt off.
Nightmare Fuel / Spider-Man: The New Animated Series
As short-lived and overlooked as the series was, the show was notably much darker than the other Spider-Man featured animated series due to having a more mature rating and having an allowance of more violence and direct death in the show, shedding light on many nightmarish scenarios.