There are several synonyms for the phrase "look full of grief". One of the most commonly used is "look mournful", which captures the sense of sadness and sorrow that the person is feeling. Other synonyms include "look crestfallen", which suggests a sense of disappointment or defeat; "look melancholy", which conveys a sense of deep sadness and depression; and "look disconsolate", which implies a sense of hopelessness and despair. Depending on the context, one or more of these synonyms may be appropriate when describing someone who appears to be full of grief. Ultimately, the choice of which synonym to use will depend on the tone and style of the writing, as well as the specific emotions being conveyed.