Below Zero achievement in Atomic Heart
This has potentially been fully fixed and now requires no upgrades to your Freeze ability
You'll need to have unlocked your freeze ability and must have upgraded it until you unlock the perk called Absolute Zero.
Without the Absolute Zero freeze upgrade, this will not unlock even if you successfully freeze a Vova in mid-air.
A Vova is the basic humanoid moustached robot that you encounter a load of.
One of the attacks it does is a charging kick attack. It will change into a running stance and come charging towards you, then when near it will launch into a flying kick.
You'll need to time this perfectly. As the Vova runs at you, you need to start freezing them at the exact second their feet leave the ground (half a second or so before the red circle telling you to dodge appears) and keep freezing until they're frozen solid.
You'll need to take a step back or to the side just as they leave the ground too, in order to avoid being damaged by the attack.
Old info that may be of use, so I'll leave it here: