The wrong conception about Absolute Zero is that it needs to be channeled to max and hit enemies to be used effectively. Yes, it could happen but it is unlikely especially if your enemies are familiar with Nunu & Willump’s kit.
The best way to make it happen is by using it under a brush when the enemy does not expect you to be there.
But most of the time, it is better used as a zoning tool when taking drakes or Baron or when peeling for teammates.