Requiring great or extreme bodily, mental, or spiritual strength
You'll put in the backbreaking work and then be upset when no one wants to eat the end product.
backbreaking, frustrating job to keep them running, especially the night sleeping car trains.
backbreaking work out of weeding with this handy little weed wand.
backbreaking labor, it was also used in the torture chamber to break backs.
backbreaking effort into the job.