much similarities, multiple leads, love triangles where you don't know who will end up together, antihero kind badass MLs, strong badass FLs, when main character likes/has quite strong relationship with demon, and many details in romance lines and characters.
eye candy cast!

spoiler:
in both dramas love triangle / square is very similar (3 close friends with similar hidden love triangle and new girl in picture, friends fall apart because of her)
though in Brahms there is another old friends love triangle for FL part .

overall Brahms characters have more depth, though as I remember Tempted has also quite promising start with "Gossip Girl" wibes. and also Tempted has more beautiful cast ))))

both are character dramas and somehow have similar vibes, with specific atmospher which catches you and makes feel you are there.
in both drama characters, their relationships and love triangles are raw realistic and deep, both drama has FL who loves art (music/sculpture) very much, wants to learn and success, and while going for that goal she gets in love triangle / falls in love (not only one time as it is usual for Kdrama FLs). But FL is not main similarity, the whole vibes, production, characters depth and storytalling style is similar.
P.S. in both drama there are great classic music soundtracks.

both flesh forwards from present to past and you don't know who which guy is the one from future.
both about friendship and love triangle, but more friendship (in both),
in both drama one of ML is introvert, kind of awkward but nice guy.
in both drama family, friendship relationships are shown very beautifully (of course one is long and other short drama but both do great job in the time they have).
in both there are smiles and tiers too.
even some scenes reminded me Reply 88

P.S. it's hard to say about any drama that it is similar and equally good as Reply 1988 but this short drama was really very close

Both dramas are about the rise of Lee Bang Won. He is main lead / main story in "King of Tears", while "My Country" has other main leads (2 young guys) but historical events are same and though as SML Lee Bang Won is one of most memorable, important and deep character.

not Arthdal level (there isn't any drama on it's level) but most close vibe I've seen in Asian dramas.
many things are close and similar, and if you don't know it is so old (2007) would think it's modern high budget drama.

long historical dramas with very similar romance part and dynamic between 2 men and 1 woman. Of course Empress Ki is more complex drama, though it has issues too.

spoilers:
in both FL is strong (of course Ki is much badass woman) girl who has lover (there's more similarities in this relationship but too much spoilers) nice brave guy, but then not so likable emperor who had long time crush on FL (from the time she didn't treated him as emperor) takes her in his harem, loves her very much and because of that she is target of other wives. She hates emperor but slowly develops feelings.
though endings are different (similar in some details but different in overall feel to Emperor).
Also Emperor in "Ki" is more nice but weak, though I think more likable character after all.

I personally loved Emperor in "Ki" and other guy (though he is less main lead then King of Korea in "Ki") in King's Woman.

not so similar but both have interesting touch to Crown Prince Sohyeon (who was ahead of his time, wanted to bring modern things in Korea).
While he is ML in 3 Musketeers, In The King: Eternal Monarch. Crown Prince Sohyeon, in a parallel universe, lived on to become king. His reign would cause a chain reaction that culminated in a modern constitutional monarchy.

both drama ask question, what would be if Prince Sohyeon became King as he should be.

If you liked Jang Hyuk as Lee Bang Won and want more - try this.

one is tv series, another movie, in both Jang Hyuk plays Lee Bang Won and is amazing. Of course same time period and historical events.

in both except for Jang Hyuk/Lee Bang Won there are 2 male leads (in tv series Jang Hyuk isn't listed as main lead, but he is quite main character and star of the show, though not only star because 2 young leads are also amazing and bromance is best ever)

Both are centred around a man out for revenge against rich powerful family.
Male leads are quite similar, smart, strategic and cold blooded.

in both dramas ML uses powerful woman from that family for revenge, slowly seduces her; same time he falls in love to another younger woman who is also related to this family (plans to marry young guy from this family).

very similar feel/vibe, both good old Kdramas with special realistic and full of emotion feel.
both are sad love stories with triangles (more in Bali), not only ending but the whole stories have this suffered sad feel.
both have great acting especially from ML (both great actors, especially Jo In Sung).

in both drama:
entertaining industry,
celebrity/actor ML and common/writer/producer FL romance,
one of them has cancer,
strong, independent FL,
likable SML.

ML's are different types, also secondary characters/relationships in Fantastic are more realistic (i think) and overall more positive vibe.

Fantastic is more emotional and multilayered, in first part you think it's more comedy-positive, but second part (more 3-5 episodes) are bomb of emotions, real feelings and realistic plot/characters phsicology, actions and reactions on events... everything...

both dramas realized in same year )))