You wait a few decades for reformers to transfer the country into a democracy or constitutional monarchy.
Except, that isn't really going to happen, because anyone with actual principles in such a system is either going to never find themselves in a position of power or, more likely, is going to win a free helicopter ride. What you will have instead is performative reform, where the military leaders who actually run things now give token concessions in a way that ultimately protects their position from any real democratic pressure. Even in the best case scenario, what you have is democracy with no culture of democracy, with a depoliticized, terrorized and cynical population who have been raised on generations of authoritarian propaganda and see democratic backsliding as normal. It takes a very, very long time and a lot of investment to fix something like that, assuming it ever gets fixed at all.
And the worst thing is, organized crime won't even be gone, because even if the regime did succeed in murdering all the gangs, rather than the more politically expedient method of cutting a deal with the gangs willing to politically support them and helping those gangs kill off their rivals in exchange for turning a blind eye to their activities, the absolute best outcome is still a power vacuum, and it's a power vacuum someone will fill, because your state-sponsored murder spree hasn't actually solved any of the underlying root problems that were driving organized crime. You have restricted the supply without reducing the demand, so really, all you've done is make organized crime more profitable for those willing to take the risk.
Again, organized crime being a problem in Latin America is nothing new. You have a bunch of countries that are well suited for growing coca and opium sharing a continent with one of the richest economies on the planet, with massive internal inequality driving a rampant addiction crisis and yet which also has a severe cultural and political aversion to any kind of harm prevention policy. The result has always been very predictable.
What's also very predictable is that War on Drugs 2 isn't going to turn out any different from War on Drugs 1. Something something definition of insanity.