The idea of being killed by a serial killer (or any killer) is very unappealing. The solution however requires a conscious shift in mentality.
If you want to avoid all possibilities of being killed by a human, you just need to erase the human race from existence. That's however only really step one.
Humans are unnaturally annoying and horny. They'll find a way to reach this plane of reality from a different one and repopulate everything. Thus you'll need to go through and commit systematic annihilation.
Alternatively, you can just right "Human" in the Book of Former Lifeforms.