Hard-boiled denoting a tough, realistic style of detective fiction set in a world permeated by corruption and deceit.
hard cases make bad law difficult cases cause the clarity of the law to be obscured by exceptions and strained interpretations; the saying may now also be used to imply that a law framed in response to a particularly distressing case may not be well-thought-out or well-based. The saying is recorded from the mid 19th century.
hard words break no bones the damage done by verbal attack is limited (compare sticks and stones may break my bones, but words will never hurt me). The saying is recorded from the late 17th century.
See also old habits die hard, between a rock and a hard place, school of hard knocks.