unyielding — unable to bend or be penetrated under pressure; hard: trees so unyielding that they broke in the harsh north winds.
arduous — Something that is arduous is difficult and tiring, and involves a lot of effort.
complex — Something that is complex has many different parts, and is therefore often difficult to understand.
complicated — If you say that something is complicated, you mean it has so many parts or aspects that it is difficult to understand or deal with.
demanding — A demanding job or task requires a lot of your time, energy, or attention.
difficult — not easily or readily done; requiring much labor, skill, or planning to be performed successfully; hard: a difficult job.
hard — not soft; solid and firm to the touch; unyielding to pressure and impenetrable or almost impenetrable.
impossible — not possible; unable to be, exist, happen, etc.
intolerant — not tolerating or respecting beliefs, opinions, usages, manners, etc., different from one's own, as in political or religious matters; bigoted.
intricate — having many interrelated parts or facets; entangled or involved: an intricate maze.
involved — very intricate or complex: an involved reply.
laborious — requiring much work, exertion, or perseverance: a laborious undertaking.
oppressive — burdensome, unjustly harsh, or tyrannical: an oppressive king; oppressive laws.
strict — characterized by or acting in close conformity to requirements or principles: a strict observance of rituals.
trying — extremely annoying, difficult, or the like; straining one's patience and goodwill to the limit: a trying day; a trying experience.
uneasy — not easy in body or mind; uncomfortable; restless; disturbed; perturbed.
unhappy — sad; miserable; wretched: Why is she so unhappy?
leisurely — acting, proceeding, or done without haste; unhurried; deliberate: a leisurely conversation.
nonpermissive — habitually or characteristically accepting or tolerant of something, as social behavior or linguistic usage, that others might disapprove or forbid.
relaxed — being free of or relieved from tension or anxiety: in a relaxed mood.
