Has a full genocide ever occurred against any ethnic group, culture, civilization etc. where there are currently no known living people from that group today? I'm talking about true genocide, so disease wouldn't count unless it was deliberately spread.
The Tasmanian aborigines were driven to total extinction after white settlement of Tasmania. Much of this was due to the introduction of new diseases, but some significant part was due to the "black wars".
Whether this was a true genocide under your definition is hard to say, but it was a true extinction, certainly contributed to by non-disease related hostile action.
The Beothuk Indians of Newfoundland, Canada were hunted to extinction.