I have a lot of passion for this franchise and all its lore. It's not like the Master Cheif hasn't been characterized well, it's just that he's never been seen like this. He is afraid to take action but has to because the world's fate depends on him doing just that. This is a soldier that's been through years of service. His experience as a soldier has brought him to this point of viewing his actions, all his actions, under a microscope because he sees the ripple effects of his previous actions or inaction. This installment sees the Master Chief taking on much more responsibility and blame than is rightfully his to take. He claims the responsibility because as the leading officer he should have commanded his partner, his soldier(Cortana his previous AI), better. This war that he's fighting now, started because of her. He made the decision that lead to her gaining the power she did to create this situation. At one point, the Chief is asked what is he fighting for, and his response, although badass, was sad and indicative of a broken soul. His answer was that fighting is all he knows. Abducted at the age of 6 and indoctrinated. The first lives he took was that of fellow soldier at the age of 14. This is someone with real emotional trauma. At Escharum's end after battling with Master Chief you see him showing great compassion to his fallen enemy and he explains it as in the end, all Eschrum was just a soldier. Hoping he had done the right thing. Questioning his choices. You can tell that this is also what the Master Chief is going through as well. Questioning his choices. He respects his enemy because he sees himself in them. Master Chief is a hero to all humans but so is Atriocs to the Banished. And whereas Atriocs is considered a monster to the humans. To the Banished, Master Chief is the Demon.