For many people Magic is divided in to black and white forms. White magic is mostly associated with good intentions while black magic is associated with evil. However all black magic is not evil as long as the spell caster has positive goals.
White magic can also be considered evil if a spell is intended to hurt someone. Ancient witchcraft practices were not based on the Principle of Threefold or Wiccan Law of return. In modern times most witches and practitioners follow this rule. However the rule is still mixed up.
You can perform a black magic love spell but in a positive way. You can end a hurtful relationship using black magic. How you do it determines whether such a spell will hurt your ex-lover or not. If you intend to make him or her suffer then you are not practicing positive black magic.
Going by the Wiccan Law of threefold, this evil will return to you three times. Black magic love spells may involve rituals and sacrifices. These will depend upon the type of mystic powers you choose. You can choose Voodoo, Obeah, Wiccan, Santeria, Egyptian and so on.
Each of these can be grouped into a negative or positive black magic practice. Negative black magic will of course result to hurting other people. You gain fulfillment if a love spell make the target miserable. Positive black magic love spell is harmless. It will help you do something without hurting your target.
In the plain meaning of the term, white magic is pure and positive. It involves prayers and amulets. You could be a follower of Voodoo, Obeah, Santeria and all the others. A common thing about them is that they comply with the Law of Threefold.
When you perform white magic as it should, it means you are informed about this law. If your goals are evil, your white magic cannot be true. That evil intention will haunt you. You can even cast a white magic spell to help a person in matters of love or anything else.