I'll try for some details, but it's been several years since I watched either "Frame of Mind" or "Violations."
What I recall being creepiest about FoM was Riker's not knowing what was reality and what wasn't. I can't of anything more disturbing than the possibility of my mind failing to give me such basic info reliably. Not surprisingly, the diseases I fear most (not that I actually go around thinking about them) are Alzheimer's and other forms of dementia.
As for "Violations," the sense of helplessness/powerlessness and the violation of one's physical and emotional boundaries make all
rape -- even sci-fi telepathic rape -- scary, creepy and horrifying.