"Overwhelming grief" refers to an intense and powerful feeling of sadness that is so strong, it becomes difficult to manage or cope with. Full definition
Though I had been fortunate enough to say goodbye to him and to prepare for the profound loss in my life, I still found myself experiencing overwhelming grief. (individualrelationshipcenter.com)
When they are, surviving family members are forced to confront overwhelming grief, shock and anxiety about the future. (kpattorney.com)
I myself, an American living in Virginia, felt lots of pressure to breastfeed and when I couldn't, dealt with overwhelming grief. (cupofjo.com)