There is no single answer to this question, though Qadgop’s looks dead on to me in terms of general populations.
It depends a lot on the user. No single drug is addictive to everyone. The best example I can think of is a friend on mine … let’s call him Bob. He’s done every drug mentioned in the thread so far, most of them multiple times. For Reasons, he had to go clean for a month. He didn’t make it, and do you know which drug it was that threw him for a loop? Cannabis, one of the least addictive drugs on the planet. He could regularly dabble with cocaine, oxy, crack and meth, but he couldn’t quit smoking weed, even with strong external motivation. The list of people on this planet who think weed is more addictive than crack is probably pretty small, but I know one guy on it.
Another dude I used to know, let’s call him Charles. Charles regularly used illegal stims, mostly coke and meth, with no signs of being addicted. This happened for well over a decade. Sadly, Charles found heroin much more addictive, and he was dead from an OD in less than a year from his first hit. He got a batch much stronger than usual, and it was game over.
Obviously, Bob and Charles would write their lists in different orders. Who is right?
I’ll also disagree with nearwildheaven. I have known multiple addicted users of crack and heroin, and very few of them were addicted to any other drugs, except nicotine. (Which they mostly mooched, and rarely bought) In the end, money spent on other drugs was just less money for crack/heroin. The only regular exception I saw was alcohol and stimulants, which wasn’t an uncommon pairing.