The antonyms for the word "un-safest" are "safest," "secure," "protected," "stable," and "reliable." Being safe and secure which implies that you are not in danger and are protected from harm. A secure environment provides a sense of stability and reliability that guarantees that you are not exposed to any adverse situations. In the safest environment, you're shielded from all the likely sources of harm, which means that you are in a safe zone where you can enjoy peace of mind without any anxiety. Therefore, by using these antonyms, one can effectively communicate the presence of safety, security, and protection that provides peace and comfort in any given setting.