That one is easy...The ketobemidone that was available in Sweden in the 70's...My GOD! Nothing before or after can ever compare. Everyone whom I've spoken to about it says it can never be equalled. Perhaps the batch that was around was a chemical mistake, or was so old that it had changed it's qualities - to the better I may say! But the strange fact is that the pharmaceutical company responsible, who for years had recommended 1/2 to 1 pill against severe pain, at the same time it deteriorated suddenly doubled it's recommendations...
Germany and Switzerland had it but was forced to ban it, and it's only left in Denmark and Sweden. USA and the U.N forced the rest of the world to ban it due to it being "he most addicting substance ever invented". The WD is worse than anything else but it's very fast. Funnily it's still the most stolen opioid from hospitals and pharmacies, beating all the other morphine-like medicines...
As second I'd say Diconal. These two are the only one I prefer to heroin...