Scripture records the misdeeds of numerous wicked people and uses various terms to describe them as evildoers. Haman is unique among all the evil people spoken of in Scripture because he is the only one for whom the Greek word διάβολος is used:
Esther 7:4 ἐπράθημεν γὰρ ἐγώ τε καὶ ὁ λαός μου εἰς ἀπώλειαν καὶ διαρπαγὴν καὶ δουλείαν ἡμεῖς καὶ τὰ τέκνα ἡμῶν εἰς παῖδας καὶ παιδίσκας καὶ παρήκουσα οὐ γὰρ ἄξιος ὁ διάβολος τῆς αὐλῆς τοῦ βασιλέως
LXE Esther 7:4 For both I and my people are sold for destruction, and pillage, and slavery; both we and our children for bondmen and bondwomen: and I consented not to it, for the slanderer is not worthy of the king’s palace.
Esther 8:1 καὶ ἐν αὐτῇ τῇ ἡμέρᾳ ὁ βασιλεὺς Ἀρταξέρξης ἐδωρήσατο Εσθηρ ὅσα ὑπῆρχεν Αμαν τῷ διαβόλῳ καὶ Μαρδοχαῖος προσεκλήθη ὑπὸ τοῦ βασιλέως ὑπέδειξεν γὰρ Εσθηρ ὅτι ἐνοικείωται αὐτῇ
LXE Esther 8:1 And in that day king Artaxerxes gave to Esther all that belonged to Aman the slanderer: and Mardochaeus was called by the king; for Esther had shewn that he was related to her.
His use of slander to try to bring about the extermination of the Jews likely explains the use of this word for him (Est. 3:8-9) because he is thus like the devil himself, who “was a murderer from the beginning,” “is a liar, and the father of it” (John 8:44), and seeks the destruction of the Jews (cf. Rev. 12:13-17).