I've read one from a Tumblr blog where we can be toxic partner and corrupting an RO, but I forgot the name of the IF.
The premise is you killed your Best Friend abusive partner, and now that you taste the thrill of killing, you can't stop anymore. One of the RO is the first victim best friend, an innocent man. I believe we can slowly manipulate and corrupting him throughout the story, at least that's what the author promised, but I haven't seen it for sometimes.
Either I forgot to follow the blog, or it got deleted. Perhaps somebody here knows the IF I'm talking about?