The term "counter-signed" refers to the act of signing a document along with another person, usually in the case of an approval or authorization. The opposite term for "counter-signed" could be "disavowed" or "repudiated", which means denying or rejecting the contents of a document or an agreement in front of a witness. The term "unauthorized" is another antonym for "counter-signed", which refers to documents that are not approved or confirmed by a superior authority. Similarly, the term "unratified" can also be used as an antonym, indicating a document that has not been officially approved or certified. These antonyms help provide clarity and precision in legal or formal situations, where the validity and authenticity of a document are critical.