The phrase "grim aspect" refers to a somber and troubling appearance. Synonyms for this phrase could include "dismal appearance," "sombre countenance," or "bleak facade." Other synonyms might include "dark demeanor," "austere features," or "gloomy expression." These words all describe similar feelings of foreboding or unease that may come with seeing something or someone that appears bleak or serious. Other potential synonyms might include "menacing appearance," "severe facade," or "dour countenance." Whatever the specific word or phrase used to describe a grim aspect, it's clear that the feeling evoked is one of apprehension and concern.