Biblical killer (4)
I believe the answer is:
cain
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">biblical killer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for cain that I've seen before include "The first known murderer" , "Adam's son" , "Eldest son of Adam, Eve" , "Eve's firstborn" , "Slayer of Abel" .)