Very good! What spirit did you chose to use? I would recommend Father Belial, Evil Chief Adramelech or Lord Azazel. And also i’m not as experienced as @AlphaC or @Ozraga or @Semyaza or @Fuego1 at killing spells i’m an apprentice at the beginning of his journey.
But you seem to have the most basic essentials for a killing curse. Here’s some useful information directly from master E.A.
Edit: I would also recommend you my personal and very sadistic demon Axa Oddra The Demon of Nadharkis - Axa Oddra / Ax Tenebrae Ornagga - #14 by anon72351403
Her talents are just perfect, as they seem to turn the victim insane and lead them trough their insanity to their death…