Actually, I will vouch for this idea. Revenge should be a double-edged sword; a more realistic revenge story should not only destroys the avenged but also destroys the avenger. Mentally, physically, and the soul. It really should be a morally grey affair. The best of Chungmuro revenge movies often shows that revenge more than often damages the one committing the vengeance deeds as well. Also noticed that many villains in Chungmuro revenge movies come with some shades of grey, not showing them as 200% devil incarnate but with some semblance of humanity. Although I know some of the worst, vile characters to ever grace cinema come from Korean revenge thrillers/movies ie. I Saw the Devil.

Even in the latest acclaimed revenge thriller, The Glory, I still found the villains are quite two-dimensional. We easily root for the main characters, of course, but basically, we wait for the villain gangs to trip over themselves so that our leads can beat them up in one sweep.
Granted, both the villains and the leads are wonderfully acted by the cast and I would not complain at all.

I think the reality is that we're not sure that bad karma will always come to those who do hateful things to other people. We see many terrible people living quite well, just as there are people full of love who are ripped from us way too soon. COVID emphasized that life is pretty fragile and random and we yearn for more control over our lives than ever. I guess if you were Christian, you can believe that there is a heaven and hell and the score will even out in the afterlife, but half of koreans have no religious affiliation.

Revenge dramas aren't new, but I think the current uptick in them -especially on primetime and more popular platforms- reflect how korean society feel like the current existing laws aren't developing enough to protect victims and how there are just too many loopholes for the rich and connected. And laws and practices also favor men versus women.

People are more sick and tired of inequality and feeling stuck. Since the average person can't vent and feel heard through existing laws (nor do they have the resources to pursue justice), they just have to vent and feel heard through watching an escapist revenge fantasy, which I guess is a lot of healthier than other ways to vent out feelings of anger, stress, and despair.