saddest korean drama or movie you ever watched?

well i cried watching 
Autumn Tale (towards the end)
Werewolf Boy  
Dont Forget me (kmovie)
A moment to remember 

Some of these may not be categorized as sad but they had me sobbing when I watched them. 

dramas: 
Scent of a Woman 
Marriage Contract 
Uncontrollably Fond 
Descendants of the Sun 
Goblin
The Master's Sun 
D-Day 
Her Lovely Heels 
Signal
W 
Dear My Friends 

movies: 
Salut D'Amour 
Classic 
Love 911 
Little Big Master (hk movie)
The Library (thai movie)

+1 Hope
Train to Busan had me crying a lake too
And Goblin

Empress Ki
I'm sorry i love you
kill me heal me
secret

I'm sorry I love you, k-version. The most heartbreaking drama I've ever came across.

These dramas had me crying my eyes out in some parts:

Descendants of the Sun
Goblin (SO depressing)
Moon Lovers

Movies:

Classic
Sunny
Train to Busan
Miracle in Cell No. 7
Windstruck
A Millionaire's First Love
Will You Be There?

I'm sorry I love you
Empress ki
Secret
Kill me heal me

Honestly you can cry in any show depending on your mindset at the time :p