Zombies

In most cases the zombies will have an imediate hunger for human flesh but in some exceptions the zombies are "good" and after some few days they turn into evil and vengeful beings

Some zombies aren't actually living corpses in the search of humans to feast on some are actually ghosts, demons or anything that doesn't need a "host" to be "alive" and will attack not anyone they encounter ,but the ones that are targets for them (like the winchesters in one episode) and they can only be defeated by using salt iron and the only real way to deal and kill is to impale them in their graves