If you're thinking of a magical spell:
* Counterspell: A spell that cancels out another spell.
* Dispel: To break or undo a magical effect.
* Anti-magic: A force that negates magic.
If you're thinking of a period of time:
* Eternity: A timeless and endless period.
* Forever: For all time.
* Continuously: Without interruption.
If you're thinking of a word or phrase:
* Explain: To make clear or understandable.
* Define: To state the meaning of.
* Translate: To convert from one language to another.
If you're thinking of a spell as a synonym for "charm":
* Repel: To drive away.
* Deter: To discourage or prevent.
* Unattractive: Not appealing or pleasing.
Please provide more context so I can give you a more precise opposite.