The heresy addressed in this letter
The group of errorists practiced a lifestyle of sexual immorality. (2 Pet 2:2,7,10,12-14,18-19 ) This wanton and arrogant display of lust was carried out on a regular basis and involved also homosexuality (cf. also Jude 4,8).
Second, the errorists “deny the Master” (= Christ; 2 Pet 2:1 Jude 4). How they did this is not clear but the Gnostic practice of cursing the earthly Jesus (see above) and exalting the serpent over Christ may give us some clue.
Third, the errorists “despise authority” and “slander celestial beings” (2 Pet 2:10 and cf. Jude 8). The context (see 2 Pet 2:11 ) indicates that these celestial beings and authorities were angels. Thus the errorists verbally attacked angels. The practice of the Cainites (see above) comes immediately to mind (see Jude 11).
Fourth, the errorists evidently taught “cleverly invented stories.” (2 Pet 1:16 ) These myths were probably Gnostic speculation about the emanation of the archons (see Chapter 7 on Gnosticism), those lower deities which-Gnostics believed-sought to prevent souls from rising at death to the high God.
Fifth, the errorists taught that there would be no second coming. (2 Pet 3:3-4 ) Such teaching is consistent with other Gnostic denials known elsewhere in the New Testament. (cf. 2 Tim 2:16-18 )
New Testament Introduction (College Press)