Recommendations

Both female lead can see ghost.
Both male lead started out by using the female lead for their own interest but fall in love with the I'm the end.
Both drama had demon/ghost taking over someone body.
Both drama had idols.
Both had badass action scene.

Both dramas are about several people living together and deal with homosexuality. They both involve siblings and address family matters.

The ability to see through the future by the female lead is the main similarity betwen both the dramas, while the male lead helps her to go through these situations.

Very similar in the topic discussed - love or money
- Both leads are willing to let go of their fortune for love
- Both parents of the the leads disprove of their relationship
- The Heirs doesn't have the betrayal aspect of the story
- Both female leads reject the money offered by the parents of the male leads - they have a similar personality, both kind-hearted
- The Heirs is more fluff less dark

War happened during japanese colonial and how woman and kids was forced to be sex slave. How they try to survive and sad story behind it.

The Lead male is popular and genius, and very cold at first until he started to like the girl. The girl likes the male lead very much (his long time crush). They also live together and student of the same school.

Similar situation: Guy doesn't have long to live, tries to get his loved one to move on. The main couple aren't married in MTB though.

Both are revenge stories with a female lead. Both heroines have had their lives stolen from them and seek to right wrongs.

Band of people get together to take down criminals. Both have criminals.
In Lookout (The Guardians) the main female lead is a cop but is a wanted criminal. In Bad Guys there is a group of criminals.

A crew of people band together to take down bad guys.
In Mad Dog the main focus is insurance fraud and in Bad Guys their is a group of criminals going after other criminals.

It's season 1 of Bad Guys so it's definitely bound to be extremely similar. Different cast. Same plot line, bad guys taking down other bad guys.

Well, not necesarilly have similar story. But the vibe of sangdoo have similarities with just between lovers. Since it's oldies drama the feeling of poor background of our hero seems more ground and real in sangdoo.

In both dramas there is a younger woman-older man relationship. The woman has some kind of sickness.

Here too the main leads meets as a teacher student. They'll face the somewhat similar difficulties. Though in doctors it's for a short span and later evolves as doctors. But still the initial sweetness and friendship between the leads is worth watching in doctors.

Both female leads can see ghosts and male leads are supernatural beings who cross path with the female leads.