The phrase "hammer blow" refers to a sudden and powerful impact, similar to the forceful strike of a hammer. It usually implies a significant or devastating event or situation that can have a profound and immediate effect. Full definition
It was driven subterranean by the thunderous hammer blows of the expenses scandal. (totalpolitics.com)
SEE ALSO: Real Madrid dealt potential hammer blow in Liga run in as two key first - teamers are laid out International midfielder reveals Barcelona are his dream club Barcelona superstar sends message to «fired» Real Madrid rival as war of words continues (caughtoffside.com)
Other revelations fell like hammer blows: Redford using government planes for a vacation; to fly her daughter and her daughter's friends around; to go to a family funeral in Vancouver. (canadianbusiness.com)