Today You Can does not consider any addiction to be “better” or “worse” than any other. With that being said, however, the American Addiction Centers report that certain drugs all increase pleasure when abused and make chemical changes in the brain to do so. Most substances of abuse interact with the production, absorption, or pathways related to the neurotransmitter dopamine, which is closely tied to how a person feels pleasure and experiences reward. Mood regulation, memory, willpower, and the decision-making processes are also impacted by drug abuse. These changes become more fixed with regular use as a drug dependency is formed. Drugs that are addictive cause difficult withdrawal symptoms and cravings, making it hard to stop taking them. Some of the hardest drugs to quit are heroin, prescription pain killers, cocaine, methamphetamine, crystal meth, benzodiazepines, and alcohol.
I hope this helped you understand what is the worst addiction.