What is the most dangerous drug known to man?

In the short-term, high-dose stimulants are quite dangerous (methamphetamine, and others), along with high-dose alcohol (due to risk of falls, head injuries, blackouts, withdrawal seizures, traffic accidents and traffic deaths, etc.). Almost half of all traffic deaths are due to alcohol.

In the long-term, cigarettes (nicotine combined with tars and many carcinogens) are the most dangerous. More people die from smoking cigarettes - than all other drugs combined (emphysema, chronic bronchitis, lung cancers, Heart disease, etc.).