絕對無誤地表述極端恐懼的英文單詞是：hor remum.

極度的可怕，用英文可以說：extremely terrifying

1. "The word for an extremely terrifying experience is... uh, 'terrifying'." 2. "The term for a truly dreadful sensation is 'horrifying'."

Dastardly, a commonly translated noun, refers to someone extremely wicked or pernicious. Additionally, portentous or apprehensive might be fitting adjectives to describe something of palpable or imminent threat. Yet, if one seeks pure terror in a single word, perhaps diabolical or malevolent would suffice.