Keener

A sharp tongue is the only edged tool that grows keener with constant use.

Source: tatoeba (26113)

A dog's sense of smell is much keener than a human's.

Source: tatoeba (615281)

There can be no keener revelation of a society's soul than the way in which it treats its children.

Source: tatoeba (3087538)

From time to time she fell into a sort of reverie, and when she was quite alone she would reason thus: "I am ill, and yet I do not know my complaint. I suffer, and yet I bear no wound. I feel afflicted, and yet I have not lost any one of my sheep. I burn, although I am seated in the deep shade. How many times have the brambles torn my skin and yet I did not cry? How many bees have pricked me with their stings and yet I was soon cured? Thus that which has now wounded me in the heart must be keener than all those!"

Source: tatoeba (6212412)