"But there were also false prophets among the people, just as there will be false teachers among you. They will secretly bring in destructive heresies, even denying the Master who bought them, and will bring swift destruction on themselves"
The word "bought" here is from the Greek, "agorazo", which refers to the "redemption" of Jesus Christ, of His blood shed for ALL sinners. This use is as defined in the standard Greek lexicons of Arndt and Gingrich, Thayer, and Robinson, and is also used in 1 Corinthians 6:20, 7:23, for this purpose. These people who are said to have been BOUGHT by the BLOOD of Jesus Christ, are REJECTING this fact, and therefore will bring "destruction on themselves", as did Judas.
See also Jude 4
"For some men, who were designated for this judgment long ago, have come in by stealth; they are ungodly, turning the grace of our God into promiscuity and denying Jesus Christ, our only Master and Lord."
Here the same word "Master", Greek, "despotes" is used for the Lord Jesus Christ. Not, as some try to get out of what it teaches in 2 Peter, by saying that it refers to God the Father.