The only thing that matters is the amount of people you execute. What's especially dumb is that you can choose which people to Purge, but no matter what options you pick, as long as you kill enough people, the civil war won't kick off.
But the idea that a large scale civil war will happen if you do not purge these people is quite literally Stalinist propaganda. Okay so I understand why players need to have some sort of incentive to carry out 'the Great Purge' in the USSR, even though historically there were no benefits whatsoever to killing off experienced generals and military staff.
