Nightmare Fuel / Mobile Fighter G Gundam

  • The Devil Gundam itself. Not only is it Satanic in name and appearance, it also infects other people and turning them into robotic zombies.
  • Earth under attack by the Devil Gundam in its Colony Mode. It destroyed a lot of cities and whatnot, offscreen deaths could have soared higher and higher in count.
  • The Devil Gundam again! Aside from the above, this could also make people fall under its command. And destroying it would be impossible even if it required a massive amount of Gundams and other mechas around only to be destroyed by it and its only death is The Power of Love.
  • Chibodee's childhood trauma. To celebrate their last day on Earth before moving to the Neo-America colony, he and his mother went to the circus. He was separated from his mother and held hostage by a terrorist dressed as a clown, all while gunfire erupted around him. His mother was likely killed, and the whole time, his captor LAUGHED MANIACALLY in the poor kid's face... *shiver*
http://tvtropes.org/pmwiki/pmwiki.php/NightmareFuel/MobileFighterGGundam