As a Canadian, I have seen a lot of disappointments among my country's athletes. The greatest disappointment was Jamaican/Canadian sprinter Ben Johnson's scandal at the 1988 olympic games in Seoul.
Johnson had said afer the race that he would have been faster if he hadn't raised his arm at the finish line. We all know later on that Johnson's urine sample contained Stanozolol and was disqualified three days later. He later admitted that he had used steroids when he set a record in 1987.
It was not rare to see athletes make use of drugs just to remain competitive.
The greatest accomplishment I have witnessed was seeing Saku Koivu returning to play hockey after his battle to cancer. I can still remember how I felt when, on September 6th, 2001, Koivu was diagnosed with Non-Hodgkin's lymphoma in his abdomen. Saku was then coming back from Finland with teammate Brian Savage, who told Koivu that he didn't look good.
When Saku returned to Montreal, he went to see Physician David Mulder. After a few tests, Koivu was diagnosed with Cancer.
Koivu was supposed to miss the remainder of the season, but thought otherwise by returning to the ice at the end of the season to help the team get a playoffs spot and go through the 1st playoff round, beating Boston in 6 games.
As for a milestone that bothered me, well, aside from Barry Bonds breaking Hank Aaron's record, I think every records are made to be broken and it doesn't bother me really.