Elizabeth Kübler-Rosss.

 In 1969, a Swiss-American psychiatrist named Elizabeth Kübler-Ross wrote in her book “On Death and Dying” that grief could be divided into five stages. Her observations came from years of working with terminally ill individuals.

https://www.healthline.com/health/stages-of-grief

The five stages of grief are:

• denial
• anger
• bargaining
• depression
• acceptance