3. To take care, pains, trouble (to do something) implies watchful, conscientious effort to do something exactly right. To take care implies the performance of one particular detail: She took care to close the cover before striking the match. To take pains suggests a sustained carefulness, an effort to see that nothing is overlooked but that every small detail receives attention: to take pains with fine embroidery. To take trouble implies an effort that requires a considerable amount of activity and exertion: to take the trouble to make suitable arrangements.

Did you mean unsparing?