death knell
noun [ S ] uk/ˈdeθ ˌnel/ us/ˈdeθ ˌnel/
终结的预兆，完结的信号
a warning of the end of something
The opening of the superstore will sound/toll the death knell for (= cause the failure of) hundreds of small independent shops. 大型超市的开张将会为数百家独立经营的小店铺敲响丧钟。