Antonyms for the word "grouchiest" would be pleasant, cheerful, friendly, happy, and easygoing. The word "grouchiest" means to be moody or ill-tempered, and any word that is the opposite of that would be its antonym. A pleasant person would be friendly, approachable, and easy to talk to, while a cheerful person would always be smiling, happy, and positive. Some people are naturally easygoing, and they take life's challenges and setbacks in stride. They are not easily offended or upset, and they are comfortable with who they are. In contrast, a grouchzilla is irritable, cranky, and negative. Life is not fun for them, and they can be a drain on others around them.