The word horrendously is an adverb that indicates something as being extremely bad, horrific, or awful. Its antonyms, or opposites, would be adverbs that indicate a less severe or negative outcome. These could include adverbs such as moderately, tolerably, satisfactorily, or acceptably. Instead of describing something as horrendously difficult or terribly boring, one could use additional words to explain the situation. For instance, someone could say the test was moderately challenging or the party was acceptably entertaining. Using a wide range of descriptive vocabulary is essential in effectively communicating one's ideas and opinions.