A convicted Colombian drug baron with links to two major cartels was shot dead in a Madrid hospital.

In what the US calls “the final, fatal blow” to the world’s biggest cocaine supplier, two Colombian brothers who helped found the infamous Cali cartel have pleaded guilty to drug trafficking, agreed to forfeit billions in assets, and received what could amount to a life sentence.

A former leader of Colombia’s defunct Medellin cartel is in a ‘‘living hell’’ of solitary confinement after being extradited to the United States to face cocaine trafficking charges, his lawyer said yesterday.