Felix Hoffman

Felix Hoffman was a German chemist, most notably famous for his development of aspirin for the first time in both a chemically stable, as well as pure state, whilst working at Bayer's, and controversially

 the development of heroin. The substance had been previously synthesised before, in 1874 England, however Bayer sold heroin up until the 1930s as a pain relief medication before research into the addictive nature of heroin was conducted and reviewed.