The word "most unwatchful" means someone who is extremely inattentive or careless. Its antonym would be "vigilant" which means someone who is alert, observant, or careful. Another antonym for "most unwatchful" is "attentive," which means paying attention to details and staying alert. In addition, "attentive" can also mean someone who is concerned about others' needs and feelings, and is ready to help. Other antonyms of "most unwatchful" could include cautious, guarded, and wary. These words convey a sense of vigilance, prudence, and watchfulness, all of which are the opposite of being careless and inattentive.