1. President Rhee from South Korea may have been corrupt and sought to change the laws to protect his own political future, but he WAS an elected figure, and was duly voted out of office the same way he got voted in. Yes, he was rumored to have ordered the extra-judicial killings of suspected communists, but I don't see much being said about him taking aggressive action against the populace at large. And for all we know, the greater populace may have supported these actions. I don't know.

2. The dictators ruling North Korea actually murdered people who were too popular within their ruling party, let alone who dared to question them. And there have been rumors that the latest passing of power came by way of murdering the predecessor.

So, I don't think it is logical to characterize South Korea as having been ruled by "a harsh dictator". The general populace had much autonomy of action, as compared to N. Korea, where there is none.