This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / Eddie Guerrero
The tribute shows in November of 2005, both taped less than a day after Eddie was found dead. If the opening salute on Raw didn't get you, the tribute video will.
Chris Benoit's death. Not only does the death erase the iconic ending of WrestleMania XX from history, but Eddie's own death played a part in it. Chris never got over it.
In particular, this part of Chris' speech during Eddie's tribute show: "He was the one friend that I had that I could go to and pour my heart out to if I was going through something, a personal issue, a personal problem. He was the one guy that I could call and talk to, and know that he'd understand and... he would talk me out of it." If Eddie had lived, it's really likely Chris Benoit, his wife and his child would still be alive today and he would still be a WWE legend.