016.
Yes, it is saddening to see someone suffering under the hands of another human being.
But I chuckle once and pity those who hold grudges and choose to take revenge on said human being.
Sure, the Hinamizawa Syndrome might not exist to drive someone in committing something as "extreme", as society considers it, as murder, but really, murder is not that great a form of revenge. Betrayal, abuse, mental and/or physical torture, or even simply "giving someone a taste of their own medicine" can all be considered far worse than murder.
Because of the lack of something like the syndrome, and because this is the modern world, people are allowed more mental coherence, time and creativity with their forms of vengeance. There are people who spend days, weeks, maybe even months imagining scenarios of how to get back at their enemies. In the end, if you are successful, what does it grant you? Materialistic issues aside, nothing, really. All it does is plague your mind when you could be doing something more useful. All it does is leave a hole in your psyche, even when you don't think it does. You don't even have to be religious to realize that.