From your definition of dangerous, you seem to be referring to
individual harm, rather than harm to others or to society, is that
correct?
As for the drug definition, I'm more confused now since alcohol
is not an illegal substance in most cultures. As it stands, I'd
have to answer that plutonium is probably a far more dangerous
drug (= illegal substance) than alcohol, but I'm sure that is not
what you are getting at.
I'll take a guess at what I think you mean and post a provisional
answer, but it may not be quite on target without more
clarification.