One of The Nine's scariest moments is the attack on Weathertop.

Watching them come in the front door with the night mist (and Barliman cowering in fear) is bad enough, but then we see a pan around the hobbit's room, and they're just there, with swords drawn and ready, like they came in through the walls or something.

The attack by the Ringwraiths on the Prancing Pony.

The screech and Vertigo Effect combination when someone encounters a NazgГ»l for the first time.

He demonstrates that those fears are well-placed, showing himself to be a One-Man Army who sends at least half a dozen soldiers flying with each swing of his mace. Just as victory seems imminent for the Last Alliance, Elrond and Isildur suddenly give expressions of fear when they see him approach, and the rest of their army quickly joins in as the Dark Lord looms over them.

Sauron joining his forces in the prologue's battle.

Their skeletal forms, visible when wearing the One Ring are really creepy as well.

He almost appears to be staring through the screen at the viewer themselves.

The Thousand-Yard Stare of the future Witch-King, at the very centre of the shot, is particularly unsettling.

And then the scene just fades as the darkness swallows them.

The shot from the prologue of the men who will become the Nazgul, each holding a ring and standing in almost robotic uniformity, in contrast to the natural movements of the elves and the dwarves in the previous shots.

And when he gives it to Bard he (according to the book) gave it 'without a shudder, without a glance of longing.' By then, he belonged to the Ring, not the Arkenstone. The Ring was also in Bilbo's possesion during that time. When he finds it's more like 'Ooh shiny.' than 'No one can have you but I.'. Remember the Arkenstone from the Hobbit? Thrain and Thorin became so obsessed with it that Thrain nearly killed himself to find it and that Thorin nearly killed Bilbo just because he gave it to them.The just out of earshot distant whispering does not help either.

Even aside from how it's barely warmed by being placed in fire and 'accidentally' ends up on Frodo's finger at the worst time, there's something fundamentally off about the seemingly-innocuous piece of jewelry. When Bilbo drops it onto the floor, it doesn't bounce and scatter into a corner, it hits the ground with a thud and goes instantly still, and when Gandalf later drops it into Frodo's palm, the hobbit's hand dips beneath its weight. If an inanimate(?) object can fall into the Uncanny Valley, it's the One Ring.Beautiful enough that you'd kill to possess it. The most beautiful thing you've ever seen in your life. The Ring would be less scary if it looked like an Obviously Evil Artifact of Doom.

It shows it doesn't need looks to take over you. You'd expect something crafted by a Dark Lord to be made of black metal with a skull-shaped ruby in the center, or something obvious like that.

Speaking of Galadriel, the genuinely unsettling calm, pleasant, soothing nature in which she acts, contrasting sharply with the demonically dark side she displays whenever she becomes angry or power-mad.

There is something so unsettling about her narration, especially when combined with the clips of darkened forests and swamps that follow.

Galadriel's 'Darkness crept back into the forests of the world' exposition.

The lord of the rings ring meme