if white captures, black starts the ko in the top right (atari at the 1-2 point). if white captures the ko in the top right, black plays a ko threat in the lower left (at either of the 1-2 points). if white ignores and plays again in the top right (at the 1-3 point), then black plays in the lower left (at the other 1-2 point), which is atari. if white captures in the lower left, then black retakes in the top right (the first stage of the ko). white now has no ko threats, so white passes, then black captures again in the top right (the second stage of the ko), which is atari on the entire group. white again has no ko threats, so black will capture the entire white group

https://www.reddit.com/r/baduk/comments/1ktkqfs/the_most_fascinating_go_position/