I'm not aware of any official Charmander horror story in the Pokémon franchise. However, there have been various fan-made horror stories and creepypastas involving Charmander, where it is depicted as a sinister and malevolent Pokémon with dark powers and a thirst for revenge.

In some of these stories, Charmander is said to have been mistreated or abandoned by its trainer, causing it to become vengeful and seek revenge on those who wronged it. In other stories, Charmander is depicted as a demonic creature that can control fire and possesses supernatural abilities.

While these stories may be entertaining to read, it's important to remember that they are not part of the official Pokémon canon and are not endorsed by the creators of the franchise. The true nature of Charmander is that of a loyal and friendly Pokémon, and it should not be feared or associated with horror.