you can make someone go insane with voodoo and make him/her kill Him/her self. It depends on how good tools you have and how sensetive the victim is for voodoo. I dont think, I know it works. But the result might not come out as hoped, It may take time and you have to be crafty.
Its about to attack from all sides, and to understand the persons weakness. But its Hard to kill at once, thats harry potter nonsense. Black magic is like warfare, you must use tactics and surprise the victim.
Hopefully, the victim dont belive in magic and the manipulation of energies, then he/she is very vulnerable.