There are entire Native American/African tribes which were probably wiped completely out with ~100s of deaths. We probably don't know much about them because they didn't have expansive empires or significant written histories of such conflicts.

We probably still do cultural eradication of small groups like this every few years even today as society modernizes.

Going back into history the early european settlers were almost completely eradicated by the invading proto-indo-europeans (90%+ genetic replacement on the Y-chromosome).