Dehumanizing describes treatment, language, or conditions that strip people of their human qualities — or that make them feel they have been stripped. A dehumanizing rule, a dehumanizing joke about a whole group, a dehumanizing workplace: the word tells you the effect on dignity, not just that something is hard. It is the -ing adjective from dehumanize, so it often sits in front of a noun (a dehumanizing experience) or after is/was (the process was dehumanizing). Same serious tone as the verb. Though actually, like the verb, it gets stretched: people call a crowded office that hands out ticket numbers dehumanizing even when no one is being treated as an enemy. That looser use is common now, and it still points at being handled as a thing rather than a person.