I think the gist of what Peter is saying in the third chapter of 2 Peter turns on the definition of a single word. On the one hand I’m reluctant to say that because it has the possibility of being overly tricky or entirely too technical, but on the other hand seeing the chapter in this light has given me a different appreciation of the entire book of 2 Peter.
Peter has been on a pretty nasty rant against antinomian gnosticism saying, among other things, that they were doomed to death and hell, that they sought to devour true believers, that they were blots and blemishes, unreasoning animals, springs without water and many other terrible things. You’ll also recall that his quarrel with them was their teaching that what one did in the flesh did not matter because the flesh could not be saved, only the spirit. As a consequence one could live as one wished because purity of the spirit was what mattered and the sins of the flesh were nothing.