read about Tarleton's supposed massacre of surrendering Continental Soldiers in the "Battle of Waxhaws" (South Carolina).
Tarleton was outsmarted a few times but didnt let that interfere with his post War political life. He became a pretty clouty PM when he returned to England in 1782.
In the pre-REvolutionary days though (even before the French and Indian Wars), the Brits AND the French AND the Colonials did kill off lotsa Native AMericans and captured several of their "forts" for its arable land .
Many of the Nations had built these palisaded towns and spent years and years "Clear cutting" so they could grow their veggies. We saw that lqnd clearing was WORK, and, true to our nature, we stole many of the fortified towns. The British were seeking to expand their empire and used all sorts of means to kill the natives or drive them off(including "Seeding" blankets with smallpox and burning crop fields). The French were mostly trying to stop the Brit advances