I like to use poppets - it’s sympathetic magic. You create a representation of the person, add a link like a signature, a bit of hair etc and convince yourself that poppet IS the person. You can make it out of anything - string, paper, (I like paperclay lately), wax, play/flour dough, cloth, depends how much help your imagination needs I guess.
Then take yarn or string, black is nice but any will do, and wrap the poppet, all the while focusing on the intention that you are literally binding up that person so they cannot harm you, affect you, that they can say nothing against you and cannot move against you. I like to make sure the bindings cover the mouth and strangle the neck. Keep wrapping and willing with as much force as you can until you feel the energy has moved into the poppet.
Finally, place the poppet in a bag and hide it at the back of the freezer, to chill them, suffocate them, and immobilise them further, but not kill them.
I heard of a ‘sweet spell’ somewhere that might be good in conjunction with this to combat the selfishness, but I haven’t done one of those personally. Might be a voodun jar spell or something.