This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Adventures of the Gummi Bears
Most of the episode "For Whom the Spell Holds". In contrast to most episodes, which are usually upbeat and colorful, this one takes place in gloomy underground caves and features fairly kid-unfriendly imagery, such as a boiling chasm and the villain's animal sidekick getting his hand burned in a realistic manner rather than as Amusing Injuries. The most disturbing moment, however, comes when Zorlock, seeking to show Zummi the price of disobedience, creates a living sculpture of a frail Gummi Bear struggling to support a globe on his shoulders, then melts it into a steaming puddle.