Which drug has the worst addiction potential?

Which of the following drugs has the worst addiction potential in terms of severity of cravings, pain & suffering of withdrawl, and lowest "complete" recovery rates?

- Alcohol
- Heroin
- Cocaine
- Methamphetamine
- Crack Cocaine

I've heard from a fifteen year old heroin addict that heroin is a drug that if you've done it once, you've done it more than once.

: http://alcoholdrugstreatment.info/which-drug-has-the-worst-addiction-potential