Although this epistle claims to have been written by Peter, he was almost certainly not its author. It is thought to have been written around 90-100 CE, long after Peter's death. The late date is suspected because verses 3:3-4 make excuses for the failure of the expected second coming of Christ, the author refers to the letters of Paul in a way that indicates that Paul's epistles were already considered equal to "the other scriptures," and the epistle depends upon the letter of Jude, which is thought to have been written around 80-100 CE.
Scholars are also agree that whoever the author or Second Peter might have been, he was not the same person who wrote First Peter. So neither of the Petrine epistles were written by Peter, and they were forged by different people. Wikipedia: Authorship of the Petrine epistles, Second Epistle of Peter
We were on the mountain when we heard the voice of God say to Jesus (1:17)
The author tries to bolster his claim to be the apostle Peter by claiming to have witnessed the transfiguration. (Matthew 17:1-8, Mark 9:2-13, Luke 9:28-36)
False prophets again, with their damnable heresies, (2:1)
The basic message of Christianity is "believe or be damned" and from this flows intolerance toward all non-Christians. But, as these verses show, Christian intolerance is often directed toward believers as well. Each group of Christians accuses the others of being "false teachers" of "damnable heresies" who will soon be damned to hell.
God didn't spare the angels who sinned but cast them down to hell.
The angels that sinned are the "sons of God" in Genesis 6:4 who had sex with the daughters of men to produce a race of giants.
He drowned everyone on earth in the flood except for Noah, a preacher of righteousness. (2:5, 3:6)
God drowned everyone on earth except for Noah [the first drunken "preacher of righteousness" (see Gen 9:20) and his family. DWB: The flood of Noah
He turned the cities of Sodom and Gomorrah into ashes. (2:6)
But saved the just man Lot ... that righteous man. (2:7-8)
Lot (who in Gen 19:8 offers his two virgin daughters to a crowd of angel rapers and later (19:30-38) impregnates them) was a "just" and "righteous man."
But he was rebuked by a donkey who spoke with a man's voice. (2:16)
The author of 2 Peter actually believes the story in Numbers (22:28-30) about the talking donkey.