agotador

adj. exhausting, gruelling, fatiguing, strenuous

n. exhauster; exhausting

= taxing, tiring, grinding, strenuous, backbreaking [back-breaking].
Ex: It is difficult to remember the special interests of more than a few people, and hence rather taxing to provide SDI manually to more than a handful of users.
Ex: Upper case can be more tiring to scan than text displayed in both upper and lower case.
Ex: Their response to the grinding monotony of repetitive labour and over-long hours was frequent absenteeism.
Ex: This article outlines the strenuous efforts to renew the library after the books had been destroyed by enemy action during World War II (the periodicals had already been evacuated).
Ex: His book plumbs the elusive depths of slaves' resistance by showing how they created opportunities for autonomy even while immersed in backbreaking work.