General Antonyms:
* Encourage
* Promote
* Foster
* Stimulate
* Support
* Aid
* Enable
* Uphold
* Permit
* Allow
Antonyms Specific to Context:
* Reveal (if talking about information)
* Express (if talking about emotions)
* Publish (if talking about writing)
* Unleash (if talking about power or force)
The best antonym for "suppress" will depend on the specific context of the sentence.