Voice Description: Killer is one of the more rare types of sanses. In his timeline, he joins forces with a genocidal Chara and kills everyone himself.

I imagine Killer to sound similar to normal sans, but more formal and soft-spoken similar to Chara. He is a psychopath, he feels nothing for anyone, not even his own brother. He speaks in a calm and rational way, despite the things he's done, does, and will continue to do.