Sycophant, false accuser!

The word ‘sycophant’ originated in the legal system of Classical Athens. Though Athens did not have a police force, it had a limited number of official public prosecutors.
Legal cases were filed by private litigants. By 500 BC, this practice had degenerated to abuse by litigants who brought unjustified prosecutions.
These litigants were called a "sycophants". Modern Greek, "slanderer"; French, "informer"; modern English, "insincere flatterer".

Flattery

5 A man who flatters his neighbor spreads a net for his own feet
Proverbs 5:6 AMPC
4 They only consult to cast him down from his height [to dishonor him]; they delight in lies. They bless with their mouths, but they curse inwardly. Selah [pause, and calmly think of that]!
Psalm 62:4 AMPC

False witness

18 The judges shall inquire diligently, and if the witness is a false witness and has accused his brother falsely,
19 Then you shall do to him as he had intended to do to his brother. So you shall put away the evil from among you.
Deuteronomy 19:18-19 AMPC

Slander, accusation

10 Then I heard a strong (loud) voice in heaven, saying, Now it has come—the salvation and the power and the kingdom (the dominion, the reign) of our God, and the power (the sovereignty, the authority) of His Christ (the Messiah); for the accuser of our brethren, he who keeps bringing before our God charges against them day and night, has been cast out!
Revelations 12:10 AMPC