For "against":
* Opposing: This is a general synonym for "against."
* Contrary to: This emphasizes a direct conflict.
* Hostile to: This implies a more aggressive opposition.
* Adverse to: This suggests a negative reaction or effect.
* Resistant to: This suggests a refusal to be affected.
For "opposite of":
* Counter: This emphasizes a balancing force.
* Inverse: This suggests a complete reversal.
* Antagonistic to: This highlights a fundamental conflict.
* Contrary to: This can also be used in this context.
For specific instances:
* Anti-war: Pacifist
* Anti-establishment: Dissident
* Anti-smoking: Nonsmoking
It's essential to consider the specific phrase or word that "anti" is attached to to choose the most appropriate synonym.