Chicago's murders are mostly gang members killing other gang members. It's cut throat black market capitalist competition.
They peddle sex and drugs mostly, so, how about an alternative, let people buy legal sex and drugs instead?
Set up legal brothels or legal bars where women or men can work the oldest profession legally.
Come up with on the books, legal production, distribution, and consumption for all the "illegal" goods.
Make them have consumer protection laws, make them pay sales tax, and treat them like any other service or product being sold on the market.
Yes, there still will be a black market, but, the participation rate will be much lower. Many criminals would go "legit", or else face dwindling market shares and income streams.