The biggest problem is drugs. The root of all evil.
I agree, drugs is the most problem ever, that's why im happy that our President was hate drugs. In that case those users and pusher will reduce. And hopefully drugs will stop every where.
It is not possible to eradicate the drug usage. Because even if you incarcerate or exterminate all the drug users, new ones will appear. The only logical solution is to increase the awareness campaigns, and to legalize the soft-drugs.