23-29% of the climbers who try K2 die in the attempt.
It is at the very least an order of magnitude more dangerous than space flight.
Just to add, Annapurna is the deadliest 8000er. With Kanchenjunga, K2 in second depending on where you get stats from.
I always thought Nanga Parbat was more deadly than Kanchenjunga.
This "Fatality Rate" compares successful summits and returns to those who die trying. Worded this way, it's a tricky number to pin down. You could be with a group that never planned to choose you as part of the smaller summit party, and still die on the mountain. But it's far from true that a quarter of people who visit the mountain die.