Tear Jerker / Friendship is Betrayal

• Under Nightmare Moon's Mind Rape, Twilight is forced to relive the events leading up to her meeting the princess... and the reason why she despises her so.
  Twilight: I'll never forget her overjoyous grin.
• Pinkie Pie's past is no better.
• Celestia confronting Luna, giving her a "The Reason You Suck" Speech, and murdering her while she's completely powerless. All while still calling her "my beloved Luna".
• FiB's spin on "Dragonshy" puts Fluttershy in a no-win situation: either she breaks her Pacifist stance and helps Twilight kill a dragon, or else she'll be labeled the traitorous spy. Even if she had enough self-confidence to explain her reasons to Twilight, she wouldn't be believed, and she knows it.
  • "Dragonshy"'s Flashback also reveals that Cloudsdale is GONE.
    • Because of Rainbow Dash's Sonic Rainboom, no less!