In the sentence "The wrestler punches his opponent in the gut," the direct object is "opponent."
What is a direct object?
A direct object is a noun or pronoun that receives the action of a transitive verb in a sentence. In simpler terms, it is the thing or person that the action of the verb is being done to.
In the sentence "The wrestler punches his opponent in the gut," the verb is "punches," and the direct object is "opponent" because the wrestler is performing the action of punching, and the opponent is the one being punched.