I agree completely and I immediately thought of Jeffrey Dahmer! To me the ending was the most graphic scene. It ended with the fact that Andy was still alive, which we then knew that Bran’s life would continue to suffer, as well as other victims. It’s repulsive in the sense that it ends like most comedies do (despite the tragic content of the story) — leaving us to know that our characters lives still continue on instead of ending definitely like tragedies do. But I think the most terrorizing thing of all is that even if Andy continued on his torturing spree, the world would continue on as if nothing happened. The victims are just another speck in the world, even if we feel that their lives are important. That being said, the same goes for Jeffrey or Andy like you said. Both are indistinguishable from the other, and are merely specks in a world.
I wasn't sure if Andy had survived or if Brandon had snapped from all the trauma and imagined Andy returning and preparing food as he always had. Since Brandon already suffered from a brain injury,(which, by the way, was well depicted with impulse control problems, rage episodes and severe mood changes) it would not be strange for him to see hallucinations as well. Which would have been a posthumous form of torture from Andy. Many survivors of violence and attempted violence report having dreams and even hallucinations of their attacker. So, Brandon, even without the TBI, could have been traumatized enough to hallucinate Andy's "return".
Which, all in all, is saying a lot. The plot and premise are both interesting and fascinating. The story takes the basic psychological profile of a serial killer and puts it into manga form. Moderate to high intelligence, holds a steady job in a respectable position, liked by coworkers and acquaintances but close friends are few, starts with animal abuse that ultimately escalates and ends in the animal's death, white male 25 - 40, aspects of the crime are ritualistic, aspects of the crime excite the perpetrator sexually, etc. If the main character's name had been Jeffrey Dahmer rather than Andy, I would not have been surprised. That said, it was well done and researched fairly well. The art was as beautiful as it was graphic. Overall, the quality of the manga was exceptional though the topic, plot, situations and themes may be repulsive to some.