What is the gender opposite of impongo?

"Impongo" is not a word with a gender opposite. It's a verb in Spanish, meaning "to impose."

Verbs in Spanish do not have genders. They are conjugated differently depending on the person and tense, but not based on a gender opposite.

Perhaps you were thinking of a different word, or you meant to ask about a noun that has a gender opposite. Please clarify your question!