Warrior Cats Omen of the Stars/Tear Jerker


 * 's death in Fading Echoes., too.
 * Anything related to Graystripe that isn't Firestar. His first mate dies, his second mate gets horrifically ill, his children die (Feathertail), run away (Stormfur), get crippled (Briarlight), or perform Face Heel Turns. He himself not only goes through this, but gets kidnapped and returns to find everyone migrated away and his old home destroyed.
 * That last line in Sign of the Moon,