You've probably already read this but...
http://www.mangago.zone/read-manga/10_years_where_i_loved_you_the_most/
10 years where i loved u the most (or sth like that) spoiler!! Btw the manhua is not completed but the novel is
.
.
.
.
.
.
.
..
.
.
.
Uke dies in the end without getting together with the doctor because he gave his organ transfer opportunity to some kid :< didnt like that ending but if ur finding an uke dying manhua then....
Have you read Dark Heaven? Both parties dealt with A LOT of pain and suffering before they got their happy ending. There's no uke/seme though. They switch often.
http://www.mangago.zone/read-manga/dark_heaven/
This one probably stuck with me the longest, well written and depressing
http://www.mangago.zone/read-manga/sakura_gari/
You might have already read this one as it’s pretty popular but if you haven’t you need to!
http://www.mangago.zone/read-manga/geu_kkeute_issneun_geos/?av=1
Another good sad one with dark tone
http://www.mangago.zone/read-manga/december_rain/?av=1
This one id recommend least cause isn’t finished and dk if it ever will be but heard it stays sad
http://www.mangago.zone/read-manga/saha_lee_uin/
http://www.mangago.zone/read-manga/new_york_new_york/
I cried a lot for all the suffering this angel of a man went through.
Any manga/hwa/hua where the uke dies or gets really really injured
(=・ω・=) currently looking for something to cry at