I first watched Neon Genesis: Evangelion as a child of 8. That show is full of nightmare fuel, but this part stuck with me:
During one of the later episodes, an experimental Eva unit rejects control and starts fucking shit up for everyone. Shinji (the protagonist) is sent in to destroy it, using his own Eva unit. He discovers, however, that one of his best friends is the pilot (although his friend isn't in control), and refuses to damage the enemy Eva. The enemy Eva gets to work trying to destroy Shinji, but the commander of the operation steps in and initiates the "dummy plug" technology. The dummy plug is essentially an autonomous fighting system for the Eva, and it immediately gets to work.
First, Shinji's unit snaps the neck of the enemy unit. This isn't enough - it then throws the enemy to the ground, rips off its frontal armour, and proceeds to violently tear out its internal organs as the blood seeps into the nearby river and sprays across nearby skyscrapers. At one point, the fist of Shinji's unit comes down and mangles the head of the enemy unit, causing its eyeballs to roll around. As if to add insult to injury, Shinji's unit identifies the entry plug (cockpit equivalent) of the enemy unit, pulls it out, and crushes it in front of Shinji's eyes, despite the fact that a good friend was in there.
All the while, the commander of the operation (who is Shinji's father) is grinning widely, elated at the efficiency of his creation.