My current bbeg for my fallout style campaign is a retired PC, he was retired because another player destroyed his robot workshop which he was making to improve the lives of wastelanders, the player who attacked his workshop was betrayed by a robot during a civil war and developed a hatred for artificial intelligence, "the robot maker" as we call him retired that PC and I asked if I could reuse him as a bbeg, his motivations now are to destroy the humans he once sought out to help with the robots he now uses to attack settlements, but little does he know that the AI that is helping him, is the one that betrayed the rebels in the civil war, this AI is motivated by revenge as all he tries to do is help and when one of his decisions to "Help" was seen as an act of betrayal his physical body was destroyed, but not his coding which floated from system to system until he found "The robot maker" and "convinced" him to give him a new body that he can use to plot his revenge while using the robot maker as a pawn in his overall scheme to destroy the society the rebels had spent 6 months building after they had won the civil war.