There was something satisfying about hearing his victims scream, seeing the terror on their faces. Human life meant nothing to him, as far as he was concerned, they would all die eventually, so he may as well enjoy it.

He did his job with sadistic glee, leaving his mark for any who dared to try to track him. Killing was part of the job, torture made it so much more enjoyable. There was something sexually satisfying about hearing their screams before he finally put them out of their misery. No one said he had to make their death a quick one. Besides, he was only doing it for her.

He was hers. He was a murderer for hire, and he loved every minute of it. He knew he was sick, and it was the best feeling in the world. 

Will have dark sexual desire scenes that may not be everyone's cup of tea, but I'll try to keep them on a somewhat decent level