Hi! I want to write a horror story. I already know what I want it to be about, I have all the characters but I have problem with one of them. The evil character is young girl (still thinking about if I should make her a psychopath or possessed by some evil entity) and I can't decide how to describe her. Fair skin and platinum blonde hair or fair skin and black hair? I am also thinking about her name. I have a couple in mind but do you know any good ones associated with evil characters or any with evil meaning? Thanks for all your answers!
Welcome to the forum! If it were me, I would write both options (appearance, psycho profile!) not as part of the main story but as a separate back story(s). It always surprises me that characters I don't immediately recognise as being significant can quickly become interesting. It can be good to let a character develop outside of the main story first, that way when you add them you avoid a lot of tell and info dropping.
Baby names websites are good for helping find names and their meanings. Behindthename.com should help you. Off the top of my head, the only negative baby names I know are -- Leah: "cow" or "weary", depending on the translation. Bethany: "house of affliction" or "house of poverty". Some sites translate it as "house of figs," but this is probably incorrect because the city of Bethany in the Bible was known as a place of lepers and the otherwise disabled. Dolores: "sorrows"
You could do both at once. Demonic possession in primitive times was their explanation for various kinds of psychological problems that they had no understanding of. So the symptoms are very similar (actually the same) as various psychological disorders, only they used a much more subjective and colorful way of describing things. The Exorcist could be about a girl possessed by a demon, or she could have been sexually molested by the man who was left to watch her briefly. The movie was carefully crafted so either explanation works. Spoiler: 27 minute analysis video of The Exorcist by Rob Ager