From Redditor u/iamnotparanoid:
The Avada Kedavera curse is the most humane way to kill someone using magic. Any large scale wizard battle would have absolutely horrifying injuries on both sides.
Remember when Harry lost the bone in his arm? Imagine if that happened to your whole skeleton while on a battle field. They can enchant glass to fly at you until you're cut to ribbons. They have plants which can constrict you to death. In the book it describes the bodies being laid out, yet they never say what the injured look like.