unspeakable

Synonyms: abominable alarming appalling atrocious awful beastly beyond words calamitous detestable dire disgusting dreadful evil execrable fearful frightening frightful heinous horrible horrid incommunicable inconceivable indefinable indescribable ineffable inexpressible inhuman loathsome monstrous nameless obnoxious odious offensive outrageous overwhelming preternatural repellent repugnant repulsive revolting shocking unbelievable unimaginable unutterable

Antonyms: good nice