What we learned about Hux from Aftermath:
We learned that he wept tears of joy as he watched a giant planet-killing beam shoot up into the sky to annihilate a planet that was home to thousands if not millions of retired and disabled war veterans.
Hosnian Prime was a hub of medicine and therapy, where people were transferred to live and build new homes and settlements.
We learned that he wanted nothing more in his life than to eradicate a government that promoted individualism and the preservation of cultures and heritages. He longed for nothing more than to erase histories, suppress individuality, and homogenize everything into one perfect order.
We got to learn so much about him in this book, because we got to see what it was that the Resistance and the Republic were fighting to protect, and therefore everything that he wants to destroy.
In other words, we learned that Armitage Hux is a Space Nazi.