nail down

another nail in someone's coffin

An event that increases the likelihood of or causes further failure.

final nail in the coffin

Something that is ultimately responsible for a previously prospective demise or failure.

hit the nail on the head

To identify something exactly; to arrive at exactly the right answer.

last nail in the coffin

Alternative form of final nail in the coffin.

nail the hammer on the head

Nonstandard form of hit the nail on the head.

the nail that sticks out gets hammered down

Those who are too different or conspicuous get criticized or sanctioned by others.