There are numerous synonyms that can be used as a replacement for the term "completely contemptuous." Some of the most popular synonyms include disdainful, disrespectful, scornful, hateful, loathing, and despising. Each of these synonyms conveys a sense of deep disdain or disgust, highlighting a total lack of respect or admiration for the person or thing in question. Other potential synonyms could include haughty, arrogant, sneering, or dismissive, depending on the context and the tone being conveyed. Ultimately, the choice of synonym will depend on the writer's specific intention and the nuances of the language being used.