The first time I spoke to my girlfriend at the time about the kink, I still hadn't fully understood it and mostly thought I was into snuff, inspired by killing sexy female enemies in Video Games (Diablo 1 Succubi, Tenchu Kunoichi and the like). So in the wake of discussing tabletop RPGs we talked about scantily clad female enemies in general and I mentioned how I find killing them rather erotic. This was rather disturbing to her and we didn't talk about it much further then. We were late teenagers then I believe.
A while later, after some downtime, Midnight Ladies was back online (
Midnight Ladies) And I did mention it to her. She was interested in seeing it and I showed her some of the pictures, which she found deeply disturbing. Even years later, she still says how some of them haunt her in her sleep and how she's afraid when I twitch in my sleep.
We did end up exploring some 'more common' kinks that mostly came from her side, including BDSM, ravishment and other things, but there was always apprehension and problems when delving too deeply. I've not really been able to fully explain things due to all of the emotional baggage.
At one point I thought my online habits had been discovered, and so I brought them up and talked about the things I got into onlien (this was several years after the initial discussion), and let's just say things went very VERY poorly.
There've been more incidents since then and they've left a very significant mark on both of us as well as the relationship in general. I've since come to accept that it's not 'all my fault' and I'm not a bad person for my tastes, but I've also learned to be very careful about who to talk to them about. I strongly suggest to approach the topic carefully, especially if more hardcore stuff is involved.