The antonyms for the word "un-attackable" are vulnerable, exposed, and defenseless. These words indicate weakness, susceptibilities, and unguardedness to attacks. If a person, object, or entity is vulnerable, it means that they are prone to damage or harm. Likewise, if they are defenseless or exposed, they have no protection against impending attacks. These antonyms can also apply to emotions and mental states, such as feeling overwhelmed, insecure, or anxious. Using these antonyms can help describe situations where there is a risk of vulnerability or an absence of protection, such as a lack of cybersecurity or a weakened immune system.