Inflict the same pain on your ex that they did to you. Make them see you in their dreams night after night. Make them hallucinate and think they see you everywhere they go. Make them have crushing guilt for breaking your heart.
Make their current relationship incredibly strained and broken.
Carve target's name on black candle. Anoint candle with approximately 6 drops of oil. Light candle for 6 minutes. Be careful not to come into contact with any of the curse potions. You are advised to wear gloves in order to prevent accidental contact.