adjective
insupportable
in-suh-POR-tuh-bul/ˌɪnsəˈpɔːrtəbl/
Too burdensome to be supported.
The drilling noise is insupportable to the pedestrian covering her ears and recoiling.

Etymology
Carrying something from underneath gives the image of bearing its weight. Applied to pain, difficulty, or unreasonable demands, “not capable of being borne” means too much to endure.
In context
my attention was fixed upon every object the most insupportable to the delicacy of the human feelings I saw how the form of man was degraded and wasted I beheld the corruption of death
More examples
- Without additional staff, the workload becomes insupportable.
- The afternoon heat is insupportable in this tiny apartment.
- She finds the loneliness insupportable after months away from home.
Similar words
- unbearable
- Emphasizes suffering that a person can no longer endure.
- intolerable
- Often suggests conditions so bad they should not continue.