Antonyms are words that are opposite in meaning to another word. The term "rat fink" is slang for a person who is sneaky, deceitful, or untrustworthy. Antonyms for "rat fink" can include words that describe someone who is honest, trustworthy, and reliable, such as "upright," "reliable," "truthful," "honest," "dependable," and "forthright." These words describe people who are transparent in their actions and intentions, and who can be relied upon to keep their word. Using antonyms to describe people who exhibit opposite traits to rat finks can help to promote positive qualities and encourage people to be more honest and trustworthy in their interactions with others.