The most dangerous mountain to climb in the world is Annapurna in Nepal. Annapurna has the highest fatality rate among the world's 8,000-meter peaks, with about 27-32% of climbers who attempt it dying in the process. The mountain is notorious for its steep rocky faces, frequent deadly avalanches, unpredictable weather, and remoteness, making rescue extremely difficult. About 61 to 72 deaths have been recorded over several hundred ascents, despite it being only the tenth highest mountain in the world at 8,091 meters (26,545 feet).
Other extremely dangerous mountains include K2, the second highest peak in the world, which has a fatality rate of around 13.7% to 25% in recent years. K2 is famous for its difficult climbing terrain, harsh weather, and the deadly "Bottleneck" icefall section. Nanga Parbat is also among the deadliest, with a historically high mortality rate and extremely challenging climbing routes.
In summary, Annapurna is considered the most dangerous mountain due to its combination of steep, avalanche-prone terrain, deadly weather conditions, and its challenging remoteness from help.