WARNING: Major Spoilers ahead for the latest episode of Game of Thrones! Continue reading at your own risk...
The Night King proved his might in that scene but, if you were paying very close attention, he also may have shown that he has another advantage over his enemies to the south. It seems as though the Night King already knew that the dragons were coming and he was able to prepare for it.
If you watch the episode again, you'll see a scene where five White Walkers are sitting on their horses, overlooking the battle going on beneath them. The Night King and two others have spears, while the other two don't.
As pointed out by BuzzFeed, there were three spears with the White Walkers. Dany brought three dragons into battle.
When the Night King threw his spear at Viserion, there was no doubt in his mind that it would bring down the beast. He knew that the weapon would work. So, it stands to reason that the White Walkers were prepared for the trio of dragons that Daenerys was bringing to the party.
If this is true, then the Night King might actually have some deeper connection to his enemies. Whether he can read the mind of Bran, or he just happens to know what the future is set to bring, this guy has a serious upper hand.