to be a/the kiss of death

To be something, such as an action, event, or association, that causes inevitable ruin or failure. An allusion to Judas Iscariot's betrayal of Jesus Christ, during which Judas kissed Jesus as a way of identifying him to those who would put him to death. The company's connection to the disgraced media mogul proved to be the kiss of death, as their sales and stock value continued to plummet. We've already had our budget cut in half—anything further will be a kiss of death for this entire project!