KJV:
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.
NKJV:
But there were also false prophets among the people, even as there will be false teachers among you, who will secretly bring in destructive heresies, even denying the Lord who bought them, and bring on themselves swift destruction.
NIV:
But there were also false prophets among the people, just as there will be false teachers among you. They will secretly introduce destructive heresies, even denying the sovereign Lord who bought them—bringing swift destruction on themselves.
Interpretation:
False teachers bring destructive heresies and swift destruction upon themselves. The verse shows that teaching false doctrine leads to destruction. They deny the Lord who bought them, rejecting the one who saved them. The verse teaches that false teaching brings swift destruction. Those who lead others astray face severe consequences. Denying the Lord results in destruction both for the teacher and those who follow.