What genre do you want (shoujo, josei, shounen, seinen, yaoi, shounen-ai, etc etc)? There are so many, so better be a bit more specific about what you're looking for.
Seinen, shounen ai, or shoujo please :'D (mostly seinen but either of the three are fine)
Hmm, for shounen-ai, (this probably has been recommended a lot) but this really is a good one: http://www.mangago.zone/read-manga/10_years_where_i_loved_you_the_most/
For shoujo, if you haven't read this one, it's really good too: http://www.mangago.zone/read-manga/shigatsu_wa_kimi_no_uso/ - it's guaranteed to make you sad.
For seinen, try these two: http://www.mangago.zone/read-manga/dokgo/ and http://www.mangago.zone/read-manga/holyland/
Seinen's angst differs from shoujo & josei, but I believe these 2 fit the angsty category because the journey to reach the end is so painful.
Also, if you like josei (the more mature version of shoujo), let me recommend you http://www.mangago.zone/read-manga/yeohye/ - this one is kinda just started & updated weekly, but the epilogue straight away gave you the tragic ending, so it'll be a painful journey to retrace the story from the beginning to that ending for sure.
Have fun suffering, lol.
Oh my god you saved my night thank you very muchh, Imma binge these right away-
...Someone give me any angst series please.
I need my weekly dose of pain (づ￣ ³￣)づ