It's also just two words. Spanish worlds tend to be longer than english ones.
"Muertos" is a direct translation of "dead".
"Evil" would be "maligno", but "terroríficamente" was used "which would be like "terrifying".
Anyway spanish translations used to change a lot the titles of the movies back in the day, most famously "die hard" is "la jungla de cristal" (directly translated as: the glass jungle) here.
I've heard that they did this because direct translations or english titles didn't work as well here, and a change in the title made more people want to watch the movie.
Nowadays this happens way less, most titles are direct translations or use their english title directly.