@bannie since there were more jdramas than kdramas (and movies), and it was one long list, i wasn't sure what to chuck, but i'd gladly un-recommend the movie adaptation of SNK/Attack On Titan, because unlike the manga and the anime series, the live-action flick was a disaster, which I wish I could unsee. That mess.-_-
I would unrecommend:
Girl of 0AM - Just boring. 
Kill Me Heal Me - Well since most people like it I can't say that it's bad but I personally didn't like it that much, even though I'm still watching it. It's just not getting to me, but it's definitely watchable. 
alexandrish:

Joseon Gunman - I can't even remember the plot. Was there one? In any case, towards the end this gets so incredibly boring.
Pretty Boy - I don't even know what to say about this. It's just bad. Don't bother, even JGS's pretty face is not worth it.
Fira:

Deep Love - pointlessly depressing
Ppoi - unless you just want to watch it for chibi Johnny's
@Azzuritis (who was skipped) and @lostinparadise

If  you plan to see an action series, don't watch Fugitive Plan B unless you want to see an action film parody, because that what it is, I don't mean it in bad way, but it is actually a parody and the action sequences are all very cheesy.

@femmedesneiges - I'm going join the choir of those who weren't all that impressed by the main female character of High School King of Savvy
@Juls

Wow, you have so many great dramas on you PTW, it would be easier to recommend what you should watch :D

I wouldn't bother with Nail Shop Paris - it is quite good in the beginning, but it quickly gets quite repetitive, every episode is basically the same, just with different people and then they also dragged some fantasy elements in it which are confusing and not really well-thought-through (does this make sense?^^)

Oh and I dropped Conspiracy In The Court after one episode because I found it really confusing and I couldn't get into the characters at all. But that's only my opinion, I've only seen one episode, you you might reconsider my suggestion to not watch it :D

Other than that I can't really say anything: I either haven't seen the dramas or I loved them really much.

@versaillesyoo Sorry about what i said about currently watching dramas but i said that because alexandrish saw only 2 episodes and i didn't thought that she
might be enjoying it. it was only my oponion about that drama! 
@Archania
I would unrecommend Blood. I only watched it til episode 8 and then I just contributed on Viki, so I have seen bits of it and the ending. There were some good elements, but the acting and the development of the story wasn't good.
And I would never recommend anyone Fashion King. It's one of my least liked dramas.
I also dropped Basketball as it went into a direction I didn't like.
High School Love On and High School King of Sawy were also not my cup of tea, but maybe someone else would like them.
Inspiring Generation started so good, but after the writer change it become a mess.
But your PTW has many other great dramas/movies :)
Its a good idea in theory but not very practical. We have our biases, I personally cant stand some actors regardless of how good the series is critically. I think having recommended users with similar likes is a better idea.
The simplest solution is to watch at least an episode before deciding, but then again sometimes some of us are so masochist that we watch all 20 episodes before deciding it sucks(I am one of those people haha)
@Timbone : Well, the same could be said for the Recommendation thread... I watched some recommended dramas and I was let down but it still help giving priorities for what to watch next. People simply don't comment if they don't have any (un)recommendation to make. As simple as that.

@Miaya : I would unrecommend Protect the Boss. I gave it a 6/10 and dropped it after 9 episodes. From what I remember, I didn't like the acting and the story wasn't that interesting. I think the comical parts were way too exaggerated.
@nastou19 I'd say Man on High Heels was rather disappointing; I was hoping for a much deeper movie than the one I got.
There were still good performances in it but I can't help but feel like it could have been so much better.

 @Anastasia I understand, sorry if I sounded rude!
@versaillesyoo

Bad Guy - an unnecessary ending.I am still regretting watching it.The only good thing about it is that you see a hot Kim Jae Wook and has a very nice OST.But dont worry,the ending will make you forget all of them.

Late Night Restaurent - just watch the japanese one instead,its a masterpiece.
Giving this thread a little bump so that someone can help @blg since I haven't seen any of those dramas, haha.
@blg only watch Five Fingers if you are in mood for melodrama, because  things do get out of hand with that one. (on a side note: I'm going to stalk your list because you have many interesting titles on it)
@versaillesyoo  thank you for reviving this thread :D

@Juls  Monster - Only watch it if you really have nothing to do or you have seen everything Lee Min Ki starred in and desperate to see him  like me :D (thank you <3)