The reason something will end or die; something causing ruin: Interviewing with them could be the kiss of death
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with kiss of death
An action or relationship that is ultimately ruinous. For example, Some regard a royal divorce as a kiss of death to the monarchy. This term alludes to the betrayal of Jesus by Judas Iscariot, who kissed him as a way of identifying him to the soldiers who came to arrest him (Matthew 26: 47–49). It dates only from about 1940 but was previously called a Judas kiss.