Absolute Zero Hyper Mode:

First, complete Chapter 8. Then, repeatedly deploy well-chosen units to the Melda Ore Plant in order to gain the Melda Key. Once you gain the key, go to the Melda Ore Plant and open the previously locked door (once you teleport there, go inside the plant and enter the locked door instead of entering the first elevator). Continue through the new area until you encounter a duck-like enemy. Defeat him and break the purple crystal behind him to gain the Absolute Zero Hyper mode. It should not be too difficult to defeat the enemy, just continue to use X's and Zero's current Hyper Mode and Action Triggers and make sure you do not attack him with an element he is currently absorbing (a message will appear at the top of the screen whenever his absorbing element changes). Defeating this enemy is a lot easier than defeating the enemy which guards X's Second Hyper Mode.