If mc dosnt has a way to identify corrupt humans. He should go to all the countries and turn into ALL nobles into bones. That would fix most of the corruption. Then a new and hopefully less corrupt nobles will appear... but a way to at least more or less identify them is look at their average populance. If a countrh its like in our dear venezuela/cuba/nothk/somalia etc...then all rich people in that country deseve to be melted from inside out slowly