Hello! Okay now, my normal cup of tea isn't Thor/Loki, but if you want to cry, you MUST read Silvertongue by epiphanyx7 (http://archiveofourown.org/works/407723). I'm not even joking. Like. It's unrequited Loki/Thor, and Thor/Jane, but oh my god. I listened to the podfic and I was awake the whole night just sobbing into my pillow. Just. Really. Read it.

Wandering Child started as a WIP on a kinkmeme somewhere, and anon eventually created an AO3 account to deal with it because it grew so big, and there were so many people reading it that the thread became impossible. (http://archiveofourown.org/works/768874/chapters/1441869) It's another agonizing loki fic.

Distortions in Time by Scarecrowlady is a gen, loki-centric fic, and all I've got to say is, read the tags and warnings (http://archiveofourown.org/works/778651/chapters/1465611)

Winterheart by Goddamnhella is amazing, if less tear-inducing. But it's amazing all the same. http://archiveofourown.org/works/1002536/chapters/1985531

the Sentinal AU by Melonbutterfly (http://archiveofourown.org/series/32671) is also less directly angsty, but subtly so. Like it's not going to hit you in the face with the pain that Loki's suffered, but it's so excellently written that it's in every word and action, and there's some amazing world building to boot.

Journey to the past by melonbutterfly is another good one, where Loki's been orphaned since birth (http://archiveofourown.org/works/740132/chapters/1377852)

Say goodbye to yesterday by melonbutterfly is ANOTHER good one, and it's groundhog day, only really painful (http://archiveofourown.org/works/603307/chapters/1087623)

Also, everything by melonbutterfly and goddamnhella is amazing. That goes without saying. I hope you enjoy!