The most recent splits of ice dance (Crone-Poilier, Samuelson-Bates) and pairs (Dube-Davisson, Yankowkas-Coughlin) teams have been shocking. That started me thinking/wondering of past break ups in FS, and they are not limited to pairs and ice dance.
To me the most shocking one still remains- Michelle Kwan splitting from Frank Caroll just before the 2002 Olympic season.
Another one was Ina-Dungjen splitting after a 4th place finish at the 1998 Olympics.
Chen Lu splitting from her coach of many years after winning a world gold (95) and world silver (96) was also shocking, and it really affected her skating in 1997.
Jamie Silverstein-Justin Pekarek break up was very disappointing to me because I really liked this ice dance team. Later Jamie went to the Olympics with Ryan O'Meara but ended the partnership (retired from skating) after just one year. That was even more disappointing.
I remember being shocked when Mishkutenok-Dmitriev split in 1994 (or was it 1995 after they skated a few pro programs?). Even though Natalia did not want to go to another Olympic, I thought she would at least want to skate professionally with Artur, but I think they split because Artur wanted to continue as eligible and Natalia did not want to anymore.
The most famous has to be Rodnina-Ullanov split after 4 world titles and an OGM, but I was not watching FS then. So it's hard to be shocked or disappointed by it, particularly since Irina won two OGMs with Zaitsev after that.