Drama/ML like Monster (2014) - very dark antihero

I wand drama or just male lead like Monster (2014, korean film)

https://mydramalist.com/6529-monster-2014

there must be romance!

I wand dark ML, not someone who is just cold or manipulative in first episodes and then becomes puppy, real dark person, maybe even killer, psycho, someone who should be villain but is ML, and FL falls for him anyway