The second, of course! - because "swift", "speedy" - ταχινός - is not "short" βραχύς: the "swift" has a more adverbial slant, expressing the condition of action, something happening swiftly, in a short time, while "short" applies more to a condition, and "destruction" is not a condition to last for a short time, but rather a final, ending point of a process. On the contrary, that this ending point may come soon and very soon is expressed by a more adverbial adjective "swift" ταχινός.
Thus, the one who not only does not repent, but on the contrary, continues to seduce others with false teachings, then they leave no reason for God to continue His forbearance and long-suffering, but invite His wrath, which is for their own benefit (for always divine wrath is for good of man upon whom this wrath is exerted), which will destroy their evil ways, for "the way of the wicked will be destroyed" (Psalm 1:6), that is to say, God does not destroy the wicked whom He continuously loves, but the "way of the wicked".
And what to do if many wicked and heretical scoundrels identify themselves with their wicked ways and ideas? It is their epistemo-ontological mistake, or oftentimes also recalcitrance based on stupidity(or vice-versa: stupidity based on recalcitrance), which God lovingly wants to correct through, sometimes painful and surgical, chastisement.