How could classic 'Scooby Doo' villains be re-imagined as threats in an apocalyptic scenario?

Classic villains like the Ghostly Ghoul or the Creeper could be amplified. The Ghoul could be releasing a spectral plague, while the Creeper might be controlling mutated creatures. Captain Cutler could be commanding a fleet of automated, zombie-like ships. The key is to give them a power that scales to a world-ending event, but still maintain their core character traits and motivations – greed, revenge, or simply mischief.