All the drugs are really bad but I think nicotine, alcohol and crack are the worse, bringing really bad consequences to our body. My mom will probably die because of those cigarettes.
Methylenedioxypyrovalerone (MDPV). Often labeled as "bath salts" to avoid distribution charges. I saw a special on 20/20 about it. It causes extreme halucinations which lead to severe panic attacks and suicidal thoughts. The drug dosen't necessarily kill you except when it's taken with other drugs, but it may make you kill yourself. Look it up on Wikipedia.
Dihydrogen Monoxide. It is a naturally occuring substance that is legal and very accessable. It can cause death due to inhalation, even in small quantities. DHMO is a major component of acid rain. On average it kills 10 people every day in the U.S. In 1998 a member of the Australian Parliament announced a campaign to ban dihydrogen monoxide internationally. It has been used by terrorists. Learn more on DHMO.org.