The New Zealand volcano whose VEI 8 eruption created a large caldera about 26,500 years ago is Taupō Volcano.
The eruption was the Oruanui eruption, also called the Kawakawa event. It occurred in the Taupō Volcanic Zone on New Zealand's North Island and is classified as VEI 8, the highest category on the Volcanic Explosivity Index. Modern dating commonly places it around 25,500 to 26,500 years ago, depending on the dating method and calendar convention.
Oruanui was the world's largest known eruption of the past 70,000 years. It released hundreds of cubic kilometres of volcanic material, including vast quantities of pumice, ash, and ignimbrite. Ashfall affected much of New Zealand, and deposits even reached the Chatham Islands, about 850 kilometres away. The eruption generated the caldera that is now partly filled by Lake Taupō.
The volcano remains active. A much smaller but still powerful eruption, known as the Hatepe eruption, occurred around 232 CE and is among the most recent major eruptions in New Zealand. Mount Taranaki, White Island, and Mount Ruapehu are separate volcanoes and did not produce the Oruanui caldera.