Damnable heresies] RV 'destructive heresies.' The word 'heresy' is passing here from its older meaning of a 'school' or 'sect' (RM) to the modern meaning of 'false doctrine': cp. Acts 24:14; 1 Corinthians 11:19; Galatians 5:20. Even denying the Lord] RV 'denying even the Master'; their evil lives were a denial of Christ's authority.
Related Commentaries of 2 Peter 2:1
2 Peter 2:1
1 But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction.