1
general::
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").
American Heritage Idioms
2
general::
Phrase(s): the beginning of the end
Fig. the start of the termination of something or of someone’s death. • When he stopped coughing and grew still, I knew it was the beginning of the end. • The enormous debt we ran up marked the beginning of the end as far as our standard of living was concerned.
McGrawhill's American Idioms And Phrasal Verbs