Wash, Serenity
Joss Whedon got robbed of this show halfway through the screening of its first season. However, this gave Whedon an opportunity to destroy his audience emotionally. Whedon took the chance and killed off his beloved lead character in the most conclusive way possible, destroying the potential of another season entirely.
Hillary Whitney, Beaches
Beaches is intended to be a heartbreaker from square one. Two best friends meet and help each other develop their lives in very different ways. Hillary gets diagnosed with a rare heart problem and dies before she can get a transplant.