How about the Jews entering the Promised Land?
Leviticus 18 (the entire chapter)tells why they were to kill every living thing there.
It also gives the Hebrews a warning.
22 Thou shalt not lie with mankind, as with womankind: it is abomination.
23 Neither shalt thou lie with any beast to defile thyself therewith: neither shall any woman stand before a beast to lie down thereto: it is confusion.
24 Defile not ye yourselves in any of these things: for in all these the nations are defiled which I cast out before you:
25 And the land is defiled: therefore I do visit the iniquity thereof upon it, and the land itself vomiteth out her inhabitants.
26 Ye shall therefore keep my statutes and my judgments, and shall not commit any of these abominations; neither any of your own nation, nor any stranger that sojourneth among you:
27 (For all these abominations have the men of the land done, which were before you, and the land is defiled;)
28 That the land spue not you out also, when ye defile it, as it spued out the nations that were before you.
29 For whosoever shall commit any of these abominations, even the souls that commit them shall be cut off from among their people.
30 Therefore shall ye keep mine ordinance, that ye commit not any one of these abominable customs, which were committed before you, and that ye defile not yourselves therein: I am the Lord your God.
If you are talking about the old testament, and implying that God commanded they kill innocents, you are missing some things.
He told Abraham generations earlier that part of the reason for the time of slavery in Egypt was to wait for the iniquity(not innocent) of the Amorites to be full. Later there are a considerable number of verses that talk about how that civilization had no respect for life and had long ago moved from less than innocent to hideously abominable and then declined from there.
Further there is reference to giants and nephilim. If there were children of crossbred angels and humans, an abomination that may have existed for hundreds of years, then the entire population was tainted with not even being human.