Well regardless of what your DNA is, if your whole tribe gets killed off by the opposition that DNA is a dead end.
Given how isolated the Neanderthals were in Europe before they had contact with anyone from the wider world in the Ice Age-and that they lived in smaller groups due to limited resources in a frigid environment-they were likely more inbred than than an Egyptian royal family, and declining in numbers by the time anyone else came along for them to breed with-their lower fertility rates got them absorbed by the more numerous H Sapiens-I doubt that wholesale massacres were the cause...