Although Spider-Man: The Animated Series had to contend with certain guidelines to be suitable for children, the series managed to include frightening elements and give scary implications. Viewers, children and adults alike, filled in the blanks to the series's darker scenarios, allowing fans to imagine their own nightmares. As such, it's fair to say that parts of Spider-Man: The Animated Series are pure nightmare fuel.
The black-suit Spider-Man was very violent and dangerous, shocking many children. Little did kids know that they would see an even scarier symbiote Spider-Man years later in the final two episodes.
In "I Really, Really Hate Clones" and "Farewell, Spider-Man," fans were introduced to an alternate dimension Peter Parker who became Spider-Carnage. This version of the web-slinger had a hard life and became overcome with hatred and vengefulness. After he bonded with the Carnage symbiote, Spider-Carnage destroyed all of Manhattan, with most citizens gone or dead. If that weren't enough to give kids nightmares, the show also showed Spider-Carnage destroying the multiverse, killing countless people across dimensions.