The word "most epithetical" can be replaced by a number of synonyms, depending on the context in which it is used. Some possibilities include "most derogatory," "most insulting," "most offensive," "most disparaging," and "most abusive." Each of these words conveys a sense of extreme negativity and criticism, and can be used to describe language or behavior that is meant to tear someone down or make them feel badly about themselves. While there may be subtle differences in meaning between these various synonyms, they for the most part can be used interchangeably to describe something that is truly vile and hurtful.