I'd argue the main subversive element in Gnosticism is that the world was created by an evil being for evil purpose and seeks to impede salvation, whereas in Christianity God did create a world that for some reason is also evil, but He nonetheless acts through it and made parts of it for the sake of trying to get us to repent and accept God via Christ, showing us mercy when our sins would see us otherwise condemned.

A good example -- if I may use a source decidedly downstream of the Bible itself -- is "Sinners in the Hands of an Angry God," where the fundamental point of it, the central image, is that God is keeping us from Hell. We would fall of our own weight, our own sin, except that God has for the moment kept us aloft in His hands and given us this chance to escape damnation, but may at any point withdraw His hands and allow our sins to drag us to Hell.

There are in the souls of wicked men those hellish principles reigning, that would presently kindle and flame out into hell-fire, if it were not for God’s restraints. There is laid in the very nature of carnal men, a foundation for the torments of hell. There are those corrupt principles, in reigning power in them, and in full possession of them, that are seeds of hell-fire. These principles are active and powerful, exceeding violent in their nature, and if it were not for the restraining hand of God upon them, they would soon break out, they would flame out after the same manner as the same corruptions, the same enmity does in the hearts of damned souls, and would beget the same torments as they do in them. The souls of the wicked are in Scripture compared to the troubled sea, Isaiah 57:20. For the present, God restrains their wickedness by his mighty power, as he does the raging waves of the troubled sea, saying, “Hitherto shalt thou come, but no further,” but if God should withdraw that restraining power, it would soon carry all before it. Sin is the ruin and misery of the soul; it is destructive in its nature; and if God should leave it without restraint, there would need nothing else to make the soul perfectly miserable. The corruption of the heart of man is immoderate and boundless in its fury; and while wicked men live here, it is like fire pent up by God’s restraints, whereas if it were let loose, it would set on fire the course of nature; and as the heart is now a sink of sin, so, if sin was not restrained, it would immediately turn the soul into fiery oven, or a furnace of fire and brimstone.

. . .

So that, thus it is that natural men are held in the hand of God, over the pit of hell; they have deserved the fiery pit, and are already sentenced to it; and God is dreadfully provoked, his anger is as great towards them as to those that are actually suffering the executions of the fierceness of his wrath in hell, and they have done nothing in the least to appease or abate that anger, neither is God in the least bound by any promise to hold them up one moment; the devil is waiting for them, hell is gaping for them, the flames gather and flash about them, and would fain lay hold on them, and swallow them up; the fire pent up in their own hearts is struggling to break out: and they have no interest in any Mediator, there are no means within reach that can be any security to them. In short, they have no refuge, nothing to take hold of; all that preserves them every moment is the mere arbitrary will, and uncovenanted, unobliged forbearance of an incensed God.

As an aside, I really enjoy the writing style of this text and I strongly think that the whole thing is worth reading. Even in this text though, I would say it is somewhat at odds with the New Testament in that it much more strongly affirms the goodness of the world in a more Old Testament style, even if it's obviously extremely New Testament in saying that the only means of salvation is with the Mediator of the Covenant, Jesus Christ. It singles out man specifically as evil and characterizes the rest of creation other than Hell, the Devil, etc. as being good and preferring to serve piety.