I believe the most fucked up character I had the pleasure of playing would be a man named Lao La Lugara whom was a mobile suit pilot who was a full on sociopath. Abused by his only known family and used as a child soldier Lao later defected from his men after killing one of his two partners. He would take out his full rage out on innocents and children and deliberately prolong a war just to feed his sick twisted sense of being. He is only alive so much as he keeps fighting without it he'd have no idea what to do. He was also, not by choice, a drugged up as well.

The others I can't explain in more detail are doctors whom experiment on anyone in order to further their research even children/unwilling patients and use drugs and or magical machines to force them into their services.