Bible is pretty specific when places get conquered by the sword. Bible never says Nimrod killed anyone. Nevertheless even assuming such does not necessarily make Nimrod an evil king. The Canaanites and Phillistines got wiped out by the sword after all by good kings like David and mighty men in the sight of the Lord like Joshua.
You need to be careful and very focused on the people and the times recorded in the Bible, what stage of God's plan they're under, what most call dispensations, whether a mandate from God is proclaimed, as it is in scripture when this is the case.
The conquering of the land by Israel was ordained of God, for the express purpose of Israel occupying the land the Lord promised and to avoid pollution of the society by Canaanite, et al, practices offensive to God. People coexisting in relative autonomy and harmony, until a "mighty man" comes along to grab some more land, cattle, grain, gold, silver or slaves, or just stick his name on the road signs, is not the way of God.
We must also be careful that, in the cases of evil rulers that are used of God, it is a matter of God taking the evil and making His pleasure come of it, without He being the primal cause, which is sin, Genesis 50:20 But as for you, ye thought evil against me; but God meant it unto good, to bring to pass, as it is this day, to save much people alive. The evil ruler can be God's punishment, simply by God letting man have his way, letting the evil events run their course, man who has forgotten him and doesn't want His way or help, "Better watch what you ask for, you just might get it," and God leaves man alone, to fall in the ditches he digs.
Most wars, at man's level, boil down to just wanting to ripoff somebody else, grand theft on a grand scale. But "thou shalt not steal." (Note that the earth and the fullness thereof are God's, His right to give land to anybody He pleases, and evict who He pleases: Israel was not stealing.)
He even wrote a book promoting it.
