If "compel" means "to force someone to do something", then the opposite could be:
* Allow: This suggests letting someone do something freely, without forcing them.
* Permit: Similar to "allow," this implies granting permission.
* Encourage: This implies motivating someone to do something voluntarily.
* Persuade: This means convincing someone to do something through reasoning or argument.
If "compel" means "to force something to happen", then the opposite could be:
* Prevent: This means stopping something from happening.
* Discourage: This implies making someone less likely to do something.
* Hinder: This means making something more difficult to do.
Ultimately, the best opposite of "compel" depends on the specific meaning in the context of the sentence.