This animation is about a new Robin (Batman's son) and Batman himself. Lots of emotions are mixed up: a father and a son, two working partners, friends, etc. As for me, the villain (AKA Deathstroke) matters nothing here in this animation, the conflicts in this movie are mainly the different opinions about how to fight crime, just the quote below:
Batman: Every day. You have to keep your center, Damian. You can't fight crime by becoming a criminal. From now on, stay close. That's an order.