oh MY Geum bi with each episode I used to drop some tears !
Moon Lovers and Empress Ki seconded.

Jewel in the Palace is also a must-watch.
im rating the sadness effect on me :")

goblin = 8/10
chicago typewriter = 9/10
secret love affair = 10/10
signal = 7/10 (some particular scenes were just too sad for me)
autumn's concerto (taiwan) = 9/10
the innocent man = 10/10
that winter the wind blows = 10/10
tomorrow with you = 8/10
Moon Lovers for sure
Faith
Beautiful Days
Sorry I love You
Tree Of Heaven
Reply 1988
Autumn Tale 
Bubblegum 
Good Doctor
Tree of Heaven 
Marriage Contract 
Oh My Geum Bi
That Winter, the Wind Blows 
The Princess' Man
The Spring Day of My Life 
Uncontrollably Fond



Queen for 7 Days :(
Mmm... On the way to the Airport is a slice of life drama that is very bittersweet and raises some profound questions about life. It may not make you cry a bucket, but it could make you question things you think you believe in. 

I think that the saddest dramas I watched were Uncontrollably Fond and Angel Eyes. I did not actually like the amount of tragedy in those two, though. Many people mentioned Scarlet Heart and I would generally agree with this recommendation, but keep in mind that sometimes it is also a slightly cheese love story.
Remember War of the Son
The kdramas that made me cry the most:

Chuno
Scent of a Woman
The Princess' Man

Fated To Love You has a happy ending, but there are some parts that will really make you ache.  I see you love Jang Hyuk, so I think you would love it, if you haven't already seen it.  

Uncontrollably Fond was a beautiful drama, but right away it says danger, danger, DANGER to my heart, so if you want to cry, feel something deeply it is the drama for you.  The male lead was phenomenal in it.    

I so agree with Autumn's Concerto, and bonus, the child actor will steal your heart in that one.  His chemistry with Van Wu felt so real to me.  

Scarlet Heart Ryeo is sad but absolutely beautiful.  


i know they are older, but seriously, these two series break my heart yet i've rewatched them a million times

o Autumn Tale

o Stairway to Heaven

Moon Lovers: Scarlet Heart Ryeo

Remember: War of the Son

Reply 1988

I'm usually a rock when it comes to releasing  emotions that I feel from dramas, but these three kdramas made me cry. Also, Coin Locker Girl and A Werewolf Boy (movies) made me cry a lot. 

i just recently rewatched Fated to Love You (Kdrama) and have to second the notion above...there are countless scenes where I am just holding my pillow and/or teary-eyed.   And then there is a segment of the show that is just really really sad and cry-worthy.     Luckily, overall,  the drama  ends positively but I was a wreck watching it all over again.   The two leads Jang Na Ra and Jang Hyuk have incredible acting ability in this show especially. 

I personally find Drinking Solo a rather realistic drama that touched on all walks of life. albeit there were comedic moments and exaggerated drama, the main plot revolved around the hardships of working life "office politics etc." and also the challenges of a unemployed "student" preparing for civil exams. Most times, the drama ended with a key message that was relatable and brought a tear to my eyes. HIGHLY RECOMMEND TO WATCH DRINKING SOLO