The phrase "be at pains" means to make a great effort to do something or to be meticulous about a task. It is often used to convey the idea of putting in a lot of effort or taking great care to produce a desired outcome. Synonyms for this phrase might include "make a concerted effort," "strive," "endeavor," "exert oneself," "go to great lengths," "put in the work," or "be meticulous." These words all convey a sense of putting in great effort and being intentional about achieving a specific result. By using these synonyms, you can convey a similar meaning to "be at pains" while still having some variety in your language.