Pretty much Chile and Brazil are the most powerful ones by far. Chile has a very sensible military and don't overspent on dumb shit like wunderwaffles, they know what they want.

And Brazil not only they have a fuckhuge size but they also have a pretty decent MIC for a South American country.
They make armored vehicles, cargoplanes, jets(Gripen E), smart bombs, missiles, basically the whole lot.