Figure 17 has a good few:
- Shou's sudden death
- Hikaru almost dying in the battle against the 7th Maguar
- Tsubasa's reaction to Sho's sudden off-screen death at the end of episode 9
- Hikaru's spiral toward death in the closing episodes - particularly as you have to watch her spend her chance at survival in order to participate in the final battle.
- And of course Hikaru really dying at the end of the last episode. Try watching the ending credits after all this and watch as what was once cheesy becomes heartbreaking.