- the way the offenders will be punished is the way they committed a crime in both(they experience the same pain/suffer they have given to others)
- the mystry behind cases is also similar
- both drama makes you hesitate that rules and justice doesn't work well in our life

- dark, thriller, mysterious.
These two are very similar, if you liked the plot twist in lost in stars and the mysterious theme behind you definitely like forgotten.
(I can't add more due to spoiler)

- both male leads are general
- both female leads are doing everything to help people
Investigating for cases
Want to recognise as their personality and hardwork not as someone's wife/fiancé
And both are smart
- revenge
- both male lead are protective and let the world burn for their beloved one

I found it very similar with when the camilia blooms because it has:
- the same actress
- the same scenario about "serial killer"
- close friends of the female lead get hurt because of her and get involved with serial killer acts

there was a scene in Soundtrack #1 where Park Hyung Sik was crying over a movie :)
werewolf boy was that movie with Park Bo Young starring^^

* both dramas have the same vibe and atmosphere
* in both dramas the media have the important part and they try to show everything online to people and we can see so many interviews about the witness of monsters or accidents
* in both dramas monsters won't die or stop if somebody shot them or try to beat them
* in both dramas there is a female lead ( one as a lawyer and one as a journalist) that wants to help people and tackle the problems

* both dramas are about monsters and have the same atmosphere of fear
* in both dramas we can see strong and badass female leads
* both dramas have cliffhangers in the end

* both dramas have badass female leads
* same vibe
* someone controls the dead body's to act as he/she wants
* there are male leads in both dramas that are cops or was and hold guns
* Shamen involved
* both have things about cursing people
* it might not count but in both dramas, there is a girl ( I call them hero) that saves others but their ending is not the same. but I could feel the same pain from them.

*in both drama main leads are cops
* both female leads are badass and stubborn
* the chemistry is really the same(they care about each other a lot)
*both male leads are sweet and lovely
(maybe the genres aren't alike but after watching happiness I found catch the ghost satisfying, I've been looking for a drama like happiness and catch the ghost was my gem)

- both male leads in these two dramas have the hidden identity for the female leads
- both female leads in the first of the drama get them wrong about what they truly are (a student who is involved in an uprising and a vet)
- both dramas have the action genre
- using guns a lot
- both dramas have the political things and the authority always attention to their benefits
-SPOILER: Endings are alike

* both give the same feeling somehow
* both females are shiny and hardworking
*both males are poor and do a lot of part-time jobs
* there's a sad connection between them in the past
*both male leads are Orphan and they lived in a church
* both male leads attempted suicide

*Zombies related
* some scenes are the same
* revenge staff
* Historical theme
* in both dramas there's a girl with arrows and bows