This is the final part of the game. At this point, you have two minutes to deplete the rest of the creature's health bar. If you fail in this and the timer reaches zero, you'll have to retry from the start of the mission. Not fun.
Finish the Supreme Hunter before the timer reaches zero!
The Critical Pain Devastator is just as effective here, so by all means use it. If you are still in Critical Mass, hit the Supreme Hunter with a Critical Pain Devastator right off the bat. The number of soldiers on the platform becomes sparse as the military works to evacuate it's troops. Quickly Grab and Consume these soldiers to max-out Critical Mass, and then get into a position to perform the Critical Pain Devastator again.
The Supreme Hunter should fall after being hit by two Critical Pain Devastators. If it survives, however, equip the Blade Power and quickly chip off the remainder of it's health.
One Thousand Suns - Mission Objective: Defeat the Supreme Hunter