Any really sad, soul crushing, heartbreaking manga/hua/wa?

Dunno if you’re looking for a complete tragedy but Secret Alliance is pretty good. I related kinda heavily to the FL in her horrible relationship and the way the creator portrays panic and anxiety in her is really accurate. At some point, the FL thinks she’s dating a girl so it’s a little bit of yuri. It’s not completely sad because everyone gets to see the light and there’s a lot of nice moments between the characters too. The art is gorgeous. I suggest you give it a read!

It's very cute and made me cry buckets
https://www.mangago.zone/read-manga/the_tale_of_goldiluck_the_black_kitten/

These are all GLs:

https://www.mangago.zone/read-manga/oniisama_e/
https://www.mangago.zone/read-manga/huijin_huayuan/
https://www.mangago.zone/read-manga/a_story_concerning_sweets/
https://www.mangago.zone/read-manga/yume_no_hashibashi/
https://www.mangago.zone/read-manga/composing_spring_in_this_room_where_cherry_blossoms_bloom/
https://www.mangago.zone/read-manga/kimi_to_tsuzuru_utakata/
https://www.mangago.zone/read-manga/kimi_ga_shinu_made_koi_wo_shitai/
https://www.mangago.zone/read-manga/haru_and_midori/
https://www.mangago.zone/read-manga/a_monster_wants_to_eat_me/
https://www.mangago.zone/read-manga/vampire_chan_junior_chan/
https://www.mangago.zone/read-manga/living_will/
https://www.mangago.zone/read-manga/kago_no_shoujo_wa_koi_wo_suru/
https://www.mangago.zone/read-manga/ohana_holoholo/
https://www.mangago.zone/read-manga/to_die_in_june_one/ (read the last two chapters here: https://www.mangago.zone/read-manga/to_die_in_june/)
https://www.mangago.zone/read-manga/this_love_that_won_t_reach/ (age gap, MC is in love with her sister-in-law; rushed and ambiguous ending)
https://www.mangago.zone/read-manga/the_story_of_a_person_who_grew_a_flower/ (short story; age gap, teacher-student relationship;hanahaki disease)
https://www.mangago.zone/read-manga/avalon_bitter_anthology/ (one-shot anthology)
https://www.mangago.zone/read-manga/shiroi_heya_no_futari/ (one-shot)
https://www.mangago.zone/read-manga/141108/ (one-shot)
https://www.mangago.zone/read-manga/aliens/ (one-shot)
https://www.mangago.zone/read-manga/saudade_ni_kuchidzukete/ (one-shot)