One of the earliest things he did was mind control Sharon Friedlander and Tom Corsi into BDSM stuff. Not on panel. It was 1984. Rape is probably the most exact real world term for that.
Magma and Empath is one of the many things people disliked about Louise Simonson's New Mutants.
I don't think he's been seen since that X-Men Heroic Age one-shot, and that was sort of a cameo. He was attacked by a technozombie Harry Leland in "Necrosha." Also a sort of cameo in "Second Coming." His last major story was when he was part of Maddie Pryor's crew in early Uncanny X-Men #500s.
It was portrayed that Amara found Empath intriguing because they shared an entitled, patrician upbringing. And I could almost buy that if it weren't for his creepy power set. In his early appearances he told Emma Frost he could MAKE her love him, and proceeded to have her groveling at his feet (while dressed in her normal fetish-wear, if I recall). Although Emma was just toying with him and playing along for a gag - as a telepath she could resist his manipulations. But being a horse-killing psychopath, she encouraged his more vicious instincts. That was who she was before Morrison declared her heroic.
I never read the issue where Amara confronted Empath for manipulating her. Does Amara feel violated? I thought in the aftermath of the Decimation they were growing close again. Of course, Amara had just seen her current BF incinerated to death in front of her, so she was emotionally vulnerable then even without Empath using his powers on her.