The Cryo Beam (Tech) skill is required to get the "Icebreaker" achievement. Use the Cryo Beam skill to freeze an enemy. Then, press A to jump and Y to perform a melee attack. The enemy has to die from this attack to get the achievement. Set the difficulty to Normal or higher or else enemies will die before freezing. You will know they are frozen when they fall to the ground, unable to move. Stop using the Cryo Beam just before the enemy's health is depleted or else it will kill them.