One-word Translation in Serbo-Croatian of "Demon"

Greetings,

I'm revising my novel manuscript and need to check the translation of one word in Serbo-Croatian.

A character is in a prison camp next to a Serbian character. When the commandant passes, the latter murmurs under his breath: "Vrag."

Is this the correct translation for the English word "demon" when used as a curse or epithet by a person who speaks Serbo-Croatian?

Is there a stronger word that would be a better curse for a reprehensible, despicable person?

I checked a Serbo-Croatian/English dictionary which confirms the word translates as "demon" or "devil" but I want to make sure it translates correctly within the context I'm using.

Thanks in advance!