The word "in-supportable" implies that something is unbearable or intolerable. Its antonym, "supportable," suggests that something is manageable or tolerable. "Endurable" is another antonym for "in-supportable" and signifies that something can be endured or survived without undue hardship. Other antonyms include "bearable," "tolerable," and "sustainable," all of which suggest that something can be supported or managed without causing undue stress or difficulty. Overall, the antonyms of "in-supportable" offer us a range of options for describing situations or experiences that are not overwhelming, difficult, or insurmountable.