The deadliness of heroin is a grave concern that cannot be ignored. It is important to find synonyms that can accurately describe the severity and danger of the drug. Some alternate phrases that may be used to describe the deadliness of heroin include lethality, peril, hazard, mortal danger, deadly poison, lethal substance, and fatal potency. Each of these words paints a picture of the seriousness of the issue and can be used to raise awareness about the dangers of heroin use. While the terminology may differ, the message remains the same: heroin is a deadly drug that can have devastating consequences.