There are numerous synonyms for the phrase "ugly as hell." Some of the most common options include grotesque, hideous, unsightly, monstrous, repulsive, unattractive, and unpleasant. Other potential synonyms to consider might include disfigured, gnarly, revolting, deformed, repugnant, homely, and offensive. These alternatives can be useful for conveying a similar level of negativity and disgust without relying on a crude or profane term such as "ugly as hell." Ultimately, the specific synonym chosen will depend on the context and the desired impact of the description.