I want a romance in which the ML is really cold and doesn't seem to care about other people and because of this he doesn't really get along with the FL at first, but, when they start liking each other or when they get together, he's really sweet to her.

Dramas that have a couple dynamic like The Smile Has Left Your Eyes or Doom at Your Service (funny that it's always Seo In Guk). It doesn't necessarily need to have a similar plot, I just want the couple dynamic to be like that: a super cold/indifferent ML who falls in love and becomes kind of "nicer".

He could also be a criminal like Jang Dong Yoon in Project Wolf Hunting but he has to fall in love and change his attitude towards the FL. Fun fact: I started wanting to watch something like this after watching that movie.