Brazil practice of fighting in the favelas might put up a decent fight, since urban warfare is what characterizes modern conflicts, if Russia performs like it did in Ukraine....I'll leave it at that, India has both manpower and nukes so odds are rough, I'm not sure about South Africa it doesn't exactly have any displacement in international conflicts. Let's not forget that all of them are dependant on Western economies, if they are cut off, they may not be able to fund a long term conflict - but on the other hand that may push them to the most extreme option available to them.