Both dramas have a similar plot basis/structure:
A man faced with injustice, seeking revenge on those who hurt himself and his family, utilises a woman (who also experienced tragedy/injustice and is seeking revenge) as the central figure in his ploys to achieve revenge.

Both dramas feature plots intricately designed to systematically bring down the enemy and ultimately get revenge for injustices suffered.

Both male leads work within the justice system Jang Do Han [The Guardians] is a prosecutor and Cha Min Joon [The Goddess of Revenge] is a lawyer.

Similar concepts:
- Observation shows
- Married couples spending time/activities/holidays apart, focusing on and discovering themselves and how this relates to their marriage.

Slight differences:
Apart Together seems to focus more on the holiday/activity aspect and has multiple married couples holidaying together.
Marriage vacation focuses more on the separation aspect and seems to feature more at home scenes.

Both involve the main character suffering an injustice and end up buying a bar/pub. It has similar instances of fighting against a larger power with a small group of friends they gain by work in their bar/pub.

The feel of the dramas are quite different with Local Hero having more emphasis on the action/fighting while Itaewon Class has more focus on friendship and youth but the overarching themes of fighting for justice and placing your trust in some friends are similar.

Very similar in concept. Both about celebrities caring for young children in an environment meant to enrich the children in order for them to learn and grow.

Both involve a medical aspect.
Both have a cute love-centred feel to the show.

I'm only 6 episodes in to Doctors but throughout all of them I was reminded of how I felt when watching Descendants of the Sun.