How brutal and violent was the Revolutionary War?

The brutality and violence of the Revolutionary War is exhibited in several massacres that occurred. First, the Cherry Valley Massacre of 1778 saw a mixture of Loyalists (to the crown) and Native Americans kill 30 noncombatant civilians.
Another example was the Battle of Waxhaws, 1780. Banastre Tarleton's Loyalist men fought the Patriots in South Carolina. During the battle, it is argued that the Patriots attempted to surrender but were massacred as they laid down their arms. This, however, has been subject to much scrutiny, as both sides seem to have valid evidence to their points.
A final example was the Paoli Massacre. In 1777, British troops launched a nighttime raid on a Patriot regiment and stabbed nearly 200 Americans while they slept.
Although I have only provided evidence of brutality against Americans by the British, there are numerous examples of American violence and brutality as well. I would suggest you become familiar with both to get a more holistic view.
https://www.history.com/this-day-in-history/redcoats-kill-sleeping-americans-in-paoli-massacre