The phrase "widow maker" refers to something or someone that is highly dangerous or potentially lethal. It suggests that encountering or being involved with it can lead to someone's death, leaving their spouse or partner a widow. Full definition
Early 911 RSs were rightly called widow makers by their keepers. (automobilemag.com)
(A nurse later said their nickname for that kind of heart attack is the «widow maker,» displaying a lack of emotional intelligence that proves while there is a time and a place for everything, it is always possible to find neither.) (inc.com)
If that company relies on hype or financings, for cash, this is outright speculation, so beware of the widow maker. (equedia.com)