“What do you want with us.” See commentary on Matthew 8:29.
“Have you come to destroy us?” Jesus Christ came to destroy the Devil and his followers and his works, and the demons who followed the Devil knew that. The Greek word translated “destroy is apollumi (#622 ἀπόλλυμι). Apollumi means “to cause or experience destruction” (BDAG Greek-English Lexicon). The Gospel of Matthew says that we are to fear God, who is the one who can “destroy both soul and body” in Gehenna (Matt. 10:28), and John 3:16, using the same Greek word, says that the unsaved will “perish,” but those who believe will have everlasting life. Romans 2:12 also says the unsaved will “perish.” The demons knew that Jesus Christ came to destroy them in the Lake of Fire after a period of burning in the Lake of Fire (cp. commentary on Matt. 8:29).