Study rates them in terms of (1) harm to self and (2) harm to others.
Most harmful to self are crack, heroin, meth, and alcohol.
Most harmful to others are alcohol, heroin, and crack cocaine.
Most harmful overall are alcohol, heroin, crack cocaine, and meth.
Least harmful includes mushrooms, buprenorphine (an opioid), LSD, ecstasy. They rate marijuana as slightly less harmful than tobacco.