“Whoever fights monsters should see to it that in the process he does not become a monster.” Friedrich Nietzsche
I have seen Intelligence Officers slowly forget their mission and principles and turn into mercenaries as they became jaded, ultimately becoming the darkness they swore to fight.
Obi Won screamed at Anakin “You have become the very thing you swore to destroy” as Vader took over in the former apprentice’s heart.
The undercover cop losing their identity as they live in violence and crime, using drugs as part of their disguise and slowly sinking into the darkness they opposed.
Learn when to walk away from the fight before you become your own enemy.