Before you are given any destructive spells or rituals, I want you to think. Think about why you want the spell/ritual. Think about the person who's life you'll ruin by casting this. Now think about the self gain you get, is it really worth it?
Acceptable - Necrosis, Terminal Illness, Blisters/boils, Causing fatal or nearly fatal accidents, Fatal sleep apnea, etc.
Unacceptable - jinxes, bad luck, moral debates, saying that it's wrong to harm another sentient being, etc.
I need to cause this person nothing but suffering, preferably as prolonged as possibly.