even that person didn't know it was them because it was actually an implanted personality making their body do things.

*snaps fingers* That's the Jedi Academy trilogy. Admiral Ackbar's personal aide has had part of his brain replaced with an Imperial-controlled computer, making him do things like sabotage Ackbar's personal B-wing to undermine New Republic credibility. The arc culminates with using the aide in a plot to kidnap the children. (The control system was conveniently located on a planet Kyp Durron blew up, so the aide was then able to confess and help foil the kidnapping.)