Un-apprehensive, meaning not anxious or worried, can have several antonyms. One of the opposite words for un-apprehensive is apprehensive, which means feeling fearful or anxious about something that might happen. Another antonym for un-apprehensive could be concerned, which implies a level of worry or anxiety about something or someone. Similarly, another opposite word could be anxious, which signifies a state of anticipation or unease. Worried, tense, nervous, and agitated are some other antonyms that can be used for un-apprehensive. Thus, the antonyms for un-apprehensive can express various degrees of anxiety, apprehension, or concern.