The antonyms for "looks stern" could include various words that describe a range of emotions and facial expressions. For instance, "looks happy," "looks relaxed," "looks friendly," "looks approachable," "looks kind," "looks gentle," or "looks amused" could all be antonyms depending on the context. Additionally, depending on the degree to which "looks stern" is interpreted, antonyms that convey an opposite intensity could include "looks giddy," "looks carefree," "looks nonchalant," or "looks indifferent." In sum, the antonyms for "looks stern" are varied and depend on the specific nuance the speaker wishes to convey.