* Possessive Pronoun: If you're looking for the opposite in terms of possession, the opposite of "hers" would be "his," "yours," "ours," "theirs," or "its". These all indicate possession by a different person or thing.
* Gender: If you're looking for the opposite in terms of gender, the opposite of "hers" would be "his".
Without more context, it's difficult to say definitively what the opposite of "hers" is.