General antonyms:
* Interested
* Concerned
* Engaged
* Passionate
* Enthusiastic
* Caring
* Attentive
More specific antonyms:
* Partial (if referring to preference)
* Biased (if referring to neutrality)
* Active (if referring to lack of action)
* Opinionated (if referring to lack of opinion)
Example:
* Indifferent to the news: Interested in the news.
* Indifferent to the suffering of others: Compassionate towards the suffering of others.
It's important to consider the specific context when choosing the most accurate antonym.