The antonyms for "most overboard" would be "most restrained," "most reserved," or "most controlled." These antonyms suggest a sense of caution, moderation, and temperance. While "most overboard" implies a lack of restraint or an excessive reaction, the antonyms suggest a more measured and thoughtful approach. By demonstrating moderation and self-control, individuals can avoid overreacting, making rash decisions, or taking actions that might be regretted later. Thus, it's important to recognize the value of restraint, as it can help us avoid extreme actions or reactions that could have negative consequences.