Fallout Equestria: Project Horizons/Tear Jerker

• The climax of Chapter 6 in the Fluttershy Medical Center, when Blackjack is forced to kill 40 foals - she doesn't have any option other than leaving them in their pods, insane. It gets even worse when, as she shuts the pods down one by one, she starts singing "Hush Now, Quiet Now".
• Gem, Mini and Taurus's deaths - particularly the brief conversation with Dying!Mini after Deus is killed. Accentuated by heavy Mood Whiplash.
• Roses' funeral.
  • Thorn's death and subsequent burial, shortly afterwards.
• The opening scene of Chapter 22. Moments after realising that Stable 99 has been infected by the raider virus, Blackjack enters a Tranquil Fury as dozens of raiders pile in on her. The hopeless battle is described in painstaking detail, as Blackjack recognises - and momentarily reminisces about - each and every stablepony-turned-raider that she kills.
• Blackjack's attempted suicide in Chapter 23.
  • Consequently, P-21's attempted suicide in Chapter 25.
• Gorgon's "i am not monsher but i look liek won" letter, and the dark Call Back later on when Blackjack is deformed by taint.
• Blackjack's tearful reconciliation with P-21 at the end of Chapter 33, and subsequently, her death.