unbearable

From Middle English unberable, equivalent to un- +‎ bearable.

unbearable (comparative more unbearable, superlative most unbearable)

1. So unpleasant or painful as to be unendurable.
   • 1945 January and February, A Former Pupil, “Some Memories of Crewe Works—III”, in Railway Magazine, page 14:

     The heat of the fire, the steam which arose from the dampening water, the hard slogging at the white-hot metal of the links, and the continual pulling of lengths of chain, were calculated to put a test on the strongest of men, and often on hot summer days they had to be sent home, for the work became unbearable.

• insufferable
• unsupportable