I Saw the Devil (2010)

Both are dealing with serial killers though I saw the devil has a revenge element in it.
Both has Cat and Mouse game between them.
(I saw the devil is much more gory and Insepctor Koo doesnt contain it)
(Inspector koo's serial kerial K kills the targets in such a way that it appears as an accident)

If you like "I saw the devil" try Inspector Koo, you might like it.

Psycho, revenge, stubborn, surviving, strategies, unexpected twists, resilient, family, innocent victims, ,

they both have the girls fiance willing to become monsters to find their lovers captors, My Beautiful Bride is not horror based and has some romance.

Another revenge movie but this time about a father who will go to any length to avenge his daughter. While I Saw The Devil is rage induced and has your adrenaline pumping throughout, Broken is rage induced but more heart wrenching. Grab a box of tissues and a cup of tea rather than popcorn for this one.

-Revenge based plots following both of the drama.
-No moral "the criminal needs to be punished by the law".
-The duality of a human being when forced out of them.