Murder. Except the King James Version, every translation of the Bible says thou shall not MURDER.
The Bible and its Laws are full of instances where people killed righteously. Be it in war, self defense or as a blood redeemer of a victim - killing by itself is not biblically wrong. The intent behind the killing is what makes it the sin.
Sorry - I get irritated at this being overly misunderstood. A woman at church won't kill a bug if she can help it because "thou shall not kill". Yes, she eats meat. Yes she wears a mask and think she's helping. Yes, I'm trying to bring her around to normalcy. No, she isn't hot.