Boys Over Flowers is the drama that got many people interested in kdramas in the first place.
For me, however, it was the drama that made me think kdramas sucked and to never watch them again.

I like Yoo Ah In's super short hair (as Han Sejoo) in Chicago Typewriter VERY MUCH.
When characters play the "noble idiot" I WANNA SMASH THE SCREEN
Dramas that everyone else loved, but I didn't like it at all:
- You Who Came from the Stars
- The Master's Sun
- My Girlfriend is a Gumiho
- Boys Over Flowers
- Rooftop Prince
- You're Beautiful
- Cinderella and the Four Knights
- Monstar
- Noble, My Love
- Birth of a Beauty
- Last Cinderella
- Blood
- Hi! School - Love On
- Innocent Man
Also, I don't like Hong sisters' dramas. I find them very boring, stupid, and predictable.
Even though I liked Goblin, the only couple I shipped was the Goblin and the Grim Reaper (+Yoo Deok Hwa). The bromance was way better than the romance and I couldn't stand Sunny.
I don't like Kim Soo Hyun and one of the reasons I couldn't stand YWCFTS is because of him.
I hated Baek In Ho in Cheese in the Trap. While everyone else was having Second Male Syndrome, I was annoyed that he had too much scenes.
And I loved The Heirs and the song Love is the Moment lol
I hated  ' I'm Sorry I Love You ' l think overrated.
I like the open end of Cheese in the Trap, everyone else seemed to hate it.
I hate when they ruin a perfectly cute drama with Chaboul sp?  *sorry* stuff in the middle, or end.  Or middle and end.  Like "Oh, my Venus."  I love that drama, and I think it's cute.  And the message it sent was more about being healthy, than thin and beautiful.  Which, as a thicker lady I appreciate the idea that he loved her when she wasn't skinny, he just wanted her to live with him a long time.  But then it got all dramatic about his family.  Bleh.  Beautiful Gong Shim was the same.  I looooved the male lead, and then it got all....bleh.  

    I also didn't like lee Min Ho in Boys Over Flowers.  I DID come to love him after watching him in Faith...but you know...different.  A sexy general is different than a prick with money.  I also pretty much dropped You're Beautiful like a hot potato when I realized she was gonna end up with *jerk who's name I don't remember." I almost never get smls....but wow I did in that one.  I did pick it up and try again...but the smls got worse.  Pretty much why I made it through heartstrings was for him.  And actually a lot of people hate that one, and I kinda enjoyed it.

   I also know that a lot of people love them, but I struggle with Jdramas, the acting is usually over the top.  Some I've made it through.   "We got married for a job" is adorable and amazing and it wasn't overdone.  But that one was meant to be understated.  But I've dropped so many cause I felt uncomfortable.  I'll stick to anime and manga for the silly over the top...ness.  

Wow that was cathartic lol.  
I don't LIKE DOTS. 
I hate how cell phone text messages can sometimes be the main turning point of the story. 
The Village: Achiara's Secret is probably one of the most overrated drama I have ever watched. The plot is suppose to be thrilling, horrifying and mysterious, which it was none at all. I already knew the killer many episodes in advance, the actors were simply wrongest of the wrong ones to use for a drama like this and not to speak about the sidestories in this drama, USELESS.

I had the feeling that I was watching a drama with an intention to entertain 10-year old kids..... If you want to bother watching horror, simply find a thai movie/drama in this genre, usually lower budget, but so much better
I like this board ;p

I didn't like Goblin, the plot was weak, the romance was creepy and Eun Tuk is the worst female character ever.. all she did was fake smile throughout the whole drama... the bromance and the ost was the only good thing about it...

I generally not like the whiny poor bubbly weak positive naggy female leads, but recently there are more strong smart female leads...

Non of my hate is directed at the actresses, it's not their fault that writers make the guy extremely complicated but they don't seem to spare much thought on the girls...
I really couldn't get the hype over Legend of the Blue Sea.. I couldn't stand the storyline and the female lead was so annoying that I couldn't bear with it 
Another one was Goblin, I didn't like the romance between Kim Shin and Ji Eun Tak. The only things that kept me going were Sunny and the Grim Reaper. The rest of the plot was so lame that I had to skip most parts
@XingBack Same goes for me the plot really was weak
Goblin wasn't that good - the age difference made it bad

Naksken -
I just finished watching Signal, which was truly excellent!  I know most people agree. but the lead actor Lee Je Hoon, I wanted to slap him and tell him to "wipe that face off your head".  He literally had the same facial expression the whole time, and that expression was like he was constipated.  Any time his character was thinking he just slowly turned his head from side to side.  Urgh.  he drove me nuts.  And all the other actors were so great.  I may have rated it a 10 instead of 8.5 if they'd cast a better lead.
Just finished watching SIGNAL which was on my dropped/on hold list (ep4) since a year. This was my third time trying to finish it. I didn't like main lead since ep 1 but later I just tried to ignore him and concentrate on the cases. I did lot of fast forwarding too.
After finishing it I don't feel like I have finished a great drama I think I should have just left it in dropped list. Now I am never going to restart a drama that I dropped recently or long time ago. I drop dramas because I couldn't take it anymore and restarting it doesn't change my views either.

Also I always try to download all episodes before watching a drama that I look forward to coz I hate getting interrupted coz of buffering/power cuts and all that.
There are many dramas that I liked in the beginning and disliked later but I ended up finishing it coz I downloaded all episodes and I thought it will get better and so. Also my drop list way too long so I try not to make it worse.
I have hard time finishing on air dramas too.

I am constantly getting in and out of drama slump but I don't exactly know why I cant stop watching so many dramas I guess coz I have nothing better to do with my life.
I can relate to this,
At first, I could not believe how great K-dramas were – until I realized
that by sheer luck I started with some really good ones. So I spent hours watching any romantic K-drama I could find. By now, I’ve watched more than 150 rom dramas (thankfully some only partially), about a quarter of them I would rate good or excellent. And I thought: Wouldn’t it be nice if other people would not have to waste their precious life time watching bad dramas? And so, this website was born.
https://dramaroma.com/about/
- Tragedy is awesome.

- Happy endings mostly suck (unless they're well done).

- SHINee's Choi Min-Ho is ugly.

- J-ROCK > J,K-POP ----> ROCK > POP

- I don't get the appeal of crime dramas, they mostly focus on irrelevant characters who appear for 1 or 2 episodes leaving the main characters under- developed... They are also episodic (mostly) so the whole drama feels like a filer.

- Character driven dramas > Plot driven dramas, I don't care about the plot if I don't care about the characters, after all, I'm here for the feels..... Exception for this is thought provoking -well done- sci-fi genres (i.e Steins;Gate anime) and convoluted fantasy genres.

- According to the point above, I can tolerate a drama if the plot doesn't make sense but the characters are good, however, I can't tolerate it if the characters themselves don't make sense, and they make stupid actions and I'm supposed to root for them.

- Bad dramas > Boring dramas.
- Descendants of the Sun sucks.

- OVERRATED DRAMAS: DOTS, Goblin, Healer, The Princess' Man, Signal.
- UNDERRATED DRAMAS: Friend, our legend.