beginning of the end, the
The start of a bad outcome (ruin, disaster, catastrophe, death), as in Joe's failing two of his courses was the beginning of the end; he dropped out soon afterward. This phrase, at first (16th century) used only to describe an approaching death, gained a new meaning after the French lost the battle of Leipzig in 1813 and Talleyrand said to Napoleon, "C'est le commencement de la fin" ("It's the beginning of the end").