I Saw The Devil Mlwbd [upd] -

As the story progresses, Soo-hyun’s obsession with revenge begins to transform him. He becomes increasingly indifferent to the collateral damage caused by leaving a dangerous predator on the loose. The film ultimately explores the idea that to catch a "devil," one must become a devil themselves, leading to a bleak and emotionally devastating conclusion. Where to Watch or Discuss

But Soo-hyun was just getting started. He would wait for Kyung-chul to find a bandage, a meal, or a moment of sleep. And then, he would appear again. He would break another bone, tear another wound, and let him go once more. i saw the devil mlwbd