The minute I saw the title of this thread, I felt pretty sure it would be the Laetitia Hubert free skate. It's routines like that that make me think that figure skaters are among the bravest people in the world (not counting rescue workers, firefighters, people in the military, and cops, of course). To keep going in public (with hundreds of millions watching on TV) after everything falls apart is an unfathomable act of sheer grit to me.
If you count simply terrible skates, Kostner and a few others would certainly be up there--the ones who single all but one of their jumps and fall multiple times. But if you consider the stakes for an otherwise top skater, I agree that Kerrigan's wipeout in 93 has to be included. That was Nancy's year to be crowned. instead, Kerrigan and a few others had an awful skate in that Worlds, and by default, the previously obscure Oksana Baiul, who had already skated and received an okay score, won. Remember how shocked she was to win? That gold medal gave her her international reputation and possibly squeezed out the tiny margin (a tenth of a point, was it?) by which she defeated Kerrigan for the Olympics the next year. Not that I'm saying she didn't deserve it, but she went from nowhere to the top on the strength of that one day's work.
Maybe because I'm so fond of Browning, I'd include his fall (or was it two falls?) from the short program in '94. He was about the best skater of his era, and instead of his winning any medal at the Olympics, the gold went to Urmanov, a correct but not great skater who never again reached any kind of pinnacle. Poetic justice, though: Browning did so well as a pro skater afterward (as well as having earned a slew of World championships, of course) that it really doesn't seem to matter at all that he was 0-for-3 in his Olympic career. There is absolutely nothing of the "heartbreak kid" about him. When I think of him and Kwan, I remind myself that Cary Grant, Greta Garbo, and Fred Astaire never won Oscars for individual film performances. It doesn't seem to have hurt their status as icons.
Watching Kimmie fall apart was painful, I agree; I don't remember what year it was, but it was very difficult to watch. It was harder than watching Alissa when she's not on. Kimmie had a triple axel and triple-triples, for Pete's sake. Somewhere in the fourth dimension, her lost jumps are wowing the likes of Amelia Earhart and Judge Crater to this day.