King of High School. I don't mind noona romance, but this one is particularly troubling because the guy was a minor. I decided to check it out months after it's finished airing because at that time I wanted something silly and stress-free to watch, and ended up loving it more than I thought I would.
not really hate, but I didn't expect to like it that much in turns out to be my favorite: Master's Sun
Beethoven Virus - I only watched it because I felt like I should give k-drama another try (didn't really love the first two I watched) and it was recommended to me. I was completely in love with this drama before the first episode was over and it remains in my Top 5! <3

Roosevelt Game - I watched it because friends were watching it, and I didn't think I would like it because it was a business/sport drama. I LOVED it, it was amazing. (Edit: this one is Japanese, though... I didn't realize this is the k-drama forum *lol*)
i think it's Master Sun for me coz i'm not a fan of So Ji Sub, especially after watching him in Memories of Bali
Secret and I Remember You.
Hana Kimi I thought it would be only cheesy and typical but the characters were so fun and the romance didn't take over the whole drama. 
Healer : i put it " on-hold" at first after watching two or three episode , but later i give it a try , and it ended up as one of my fav dramas of all the time ♥

Empress Ki : the length , i saw this drama in recs and i found it a high-rating drama , but i found it too long to watch and it's historical and i was not into historical dramas, but man !!! after i give it a chance because of Ha Ji Won and Ji Chang Wook , how can this drama be so perfect ?!! i still don't know :D

You Who Came from the Stars : i don't remember the reason that made me afraid to watch this drama or why i thought it will be boring !, this one is great and so romantic !

Falling for Innocence : and that's something i can't forgive myself for , how could i think this drama will be boring ?!!!!!! , it became one of my fav and i will never forget this one, it's funny and cute ♥

Full House (Thai Version) : i was worried about it since it's a thai drama , but i loved it so much ♥

Marriage, Not Dating : i thought it will be boring , but i was wrong it's funny, crazy and cute

and Finally, Last Cinderella : it's a Japanese drama , but it was my first drama ever , and which made me fall in love with drama land, i was worried about watching a Jap drama, i thought it's weird, but i was totally wrong ! , this drama is BEAUTIFUL, cute , romantic , and have one of most handsome men in Asia Miura Haruma ♥♥♥♥
Brain: This was when I discovered what a good actor Shin Ha Kyun is.

Local Hero: Didn't really appeal to me especially since I've watched Masked Prosecutor but its actually really good. It has a reasonable MC (which is something we dont see often) and likable villains.

Pride and Prejudice: It isn't amazing but it isn't boring either. It's still pretty good, so far.

and Missing Noir M: This is what got me back into the Korean Crime/Detective genre, nothing major really happens in season 1 but that goes to show that there's a big chance of a season 2 being produced.
Bridal Mask :D It's my most favorite drama, but at first I dismissed it, since I hadn't watched anything historical before. But after I gave it a try, I absolutely fell in love even though I didn't liked the female lead. The bromance was so good.
School 2013. I thought it would be a boring school drama, since the plot description didn't appeal to me. Then I tried a KBS World App and a episode of School 2013 was showing. The scene showed made me really curious about the drama, since it seemed so much more interesting than what the plot stated. Become also one of my favorite dramas :D
Shut Up Flower Boy Band. The plot seemed really cool, but the first scene confused me so much with all the shaking and so on that I first thought I would drop it. But after watching it again and completing the first episode, I noticed how much I already liked it. And also as the dramas above: one of my favorite dramas.
Looking at the dramas I gave a high ranking, there are a few more, that I thought, I wouldn't like, but ended up loving: Angry Mom (set up seemed so silly and like a comedy), Signal
Aand honorable mention to Moorim School, which was in no way a great drama, but it peaked my interest more than I thought, although Hongbin's acting was horrible :D
You who came from the stars and my girlfriend is a gumiho. didn't like the cast (except no min woo) so put them off for ages and actually really liked it.
queen In Hyun's man, going into this drama I was quite wary, because I have never really enjoyed time travel. But unexpectedly I ended up enjoying this show.
Coffee Prince.
I really was only into J-dramas at the time and my previous experiences with a few K-dramas had been disastrous, So I started it out of boredom, expecting over the top acting, starry looks and pouting females.
It's one of my all time favourites now.
I think I'll be forever grateful to this drama for making me jump the strait and discover the world of K-drama too.
The greatest Love. omg  are the 1st two episodes awful, you just have to grit your teeth and bare it. 
history of the salaryman

heard it through the grapevine

incomplete life

iris
Queen of Ambition
Successful Story of a Bright Girl
Stairway to Heaven
My Beautiful Bride, so far its a 10/10