Norfolk Boobook (Ninox novaeseelandiae undulata) got down to a single female in 1986. A male Morepork (Ninox novaeseelandiae novaeseelandiae) was introduced and they successfully bred. The female died in 1996, at the time there were a dozen hybrid birds on the island, and the population is still there. I don't know if that's a win or not, the species is extinct but the genes are still present.
The Cromwell Chafer Beetle (Prodontria lewisi) is only found in one 81 hectare reserve and would likely be extinct now without this habitat protection.
The Cromwell Chafer Beetle (Prodontria lewisi) is only found in one 81 hectare reserve and would likely be extinct now without this habitat protection.