General antonyms:
* Liberating
* Freeing
* Emancipating
* Empowering
* Liberating
* Just
* Fair
* Equitable
* Supportive
* Encouraging
Antonyms specific to certain contexts:
* Tolerant (for "oppressive" meaning intolerant)
* Gentle (for "oppressive" meaning harsh or cruel)
* Light (for "oppressive" meaning heavy or burdensome)
* Refreshing (for "oppressive" meaning stifling or suffocating)
* Beneficial (for "oppressive" meaning harmful or detrimental)
The best antonym will depend on the specific context in which "oppressive" is being used.