Faultlessly

However faultlessly these tasks were achieved, she never commended: it was a maxim with her that praise is inconsistent with a teacher's dignity, and that blame, in more or less unqualified measure, is indispensable to it.

Source: tatoeba (8110128)

The interior of the "castle" was as faultlessly neat as its exterior was novel. The entire space, some twenty feet by forty, was subdivided into several small sleeping-rooms; the apartment into which he first entered, serving equally for the ordinary uses of its inmates, and for a kitchen.

Source: wiktionary

It is much easier to detect a fault than to produce a harmonious arrangement. And it is much easier for a man to see faults in a lady’s dress than to give directions for dressing faultlessly.

Source: wiktionary

{{quote-text|en|year=1904|author=w:Henry James|title=The Golden Bowl|passage=To the casual eye a mere smart and shining youth of less than thirty summers, faultlessly appointed in every particular, he yet stood among his progeny […] }

Source: wiktionary