An outfit is only going to be as strong as the government they have ingratiated themselves with, and no stronger than that government is itself.
Because Italy seems to be so anti-organized crime, that would eliminate any and all mainland Italian syndicates from the top of the list because not being in the favor of their home governments puts them on shaky ground.
I have read that Bolivian drug traffickers will not leave the borders of their country to transport drugs....because production of cocaine is (or was) legal...within their country. That makes their organizations pretty strong.
In another example, Canadian Cosa Nostra seems stronger than American Cosa Nostra at this time, due to the differences in the way crimes are prosecuted in the US versus Canada. In Canada things are easier for an outlaw, therefore they are probably stronger. What does it matter how many made men you have, how many guns you have, and how much money you make...if you are under indictment???
It really might come down to who has the blessing of their government and how strong their government is.
I would say the Caruana and Cun-trera mafias are right at the top.
I can't make a fair comparison of OC groups against one another world wide because I've never looked up the list. All I can do is put forward my formula for what makes an outfit truly "tough".
It's a futile question because there are many factors that make up a threat potential of organized crime groups. Some have even been put into a working formula, like the Slepnir Matrix, by law enforcement. But it's not tennis rankings.
It's debatable how anti-Mafia Italy really is, even if it's come along way, but the fact the Mafia there has thrived for so long, even if Italy has been very anti-Mafia, it should be self evident that your comment about the Italian groups isn't the case. They have been around for years and years and won't be going away anytime soon.
Meanwhile, one could argue there was even more corruption and instability in Colombia in the 1980s and 1990s. According to your theory, that should have enabled the Medellin and Cali cartels to last. But that wasn't the case.
I think if it wasn't for the immense pressure the US put on the Colombian government, they would've been around a lot longer that's for sure.
