Malice. If you asked any human, they would just say that it was evil intentions. I was the same, it was a word I knew but hardly gave any importance to. At least that was the case before I died.
Now? Malice unknowingly became a part of my life. It manifested itself in my life against my will. It was both a shackle and a warning. Taken to the extreme, I consider it even as a punishment.
By the definition of Reapers, it was considered as the collected negative feelings that being possessed when they were alive. And whenever that being dies how he died affected where the malice went.
If he was killed the malice would flow into the one who killed him. Should that being perish of natural causes or without intent it flows back to the world. Phillip even shared that Hellsgate was basically a garbage dump of malice.