What is the worst kind of illegal drug?

I was wondering, what is the worst kind of illegal drug? By “worst” I’m talking about the severity of withdrawal from the drug, how reinforcing they are (one use makes you want to do it again), how much tolerance they create (you need to use more and more each time), how much dependence they create (you need to keep using the drug or you’ll feel withdrawal symptoms). The drugs I’m wondering about would be heroin, acid, meth, cocaine/crack- all of the “hardcore”, illegal drugs. All answers are appreciated, I’m just trying to get informed(:

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