Michael was perfect. Chuck had created him as a being of perfect justice and chivalry. Chuck had created him with His Plan in mind, knowing that He would need someone to defend and guide His creations. Imperfect as the humans would be, Chuck had been completely secure in his belief that, with the right push, they'd rise to the occasion. He had banked on the idea that Michael would be just as enthusiastic about the Plan as Chuck himself.
And in the beginning, he had been. Michael had been as perfect a child as he'd been an archangel, and he followed Chuck and listened with great interest as the Plan was explained to him, as was his role in it. When Chuck created more angels, before the first humans, He had watched with pride as Michael took it upon himself to take them under his wing, and show them the way. Michael had helped in deciding the roles and merits of his three immediate brothers, as well, and Chuck had personally though he'd been very thoughtful and diligent with the whole process. He took heart, seeing what His eldest was doing, and thinking of what he would accomplish.
But too soon, the driving force that fueled the Archangel of Protection and Guidance was halted indefinitely with the Fall of his closest brother, Lucifer. And Michael became a machine.
Lucifer was Michael's first brother. The fourth being in existence, after Michael, Amara, and Chuck himself. Michael had been ecstatic to have a peer, and the two had been inseparable from the moment they'd met. But when Lucifer broke away—Michael defending humanity as he was meant to, even against his brother—Chuck suspected that if there were anyone who could possibly understand the pain He went through, it was Michael.
He stopped smiling. He became militaristic. He allowed himself no dealings with any more of his younger siblings unless it was related to business or orders to be followed out.
And then Chuck left. He regrets it now, but that's neither here nor there. But when He left, He still kept an eye on things from time to time, and His heart broke more with each glimpse.
Michael's existence had become focused on one thing, one plan. His purpose, which had once been to ensure the preservation of mankind, was not to destroy the brother he'd loved the most.
Loss—the first loss in the history of Creation—had broken the Archangel Michael.