>>90856456RECALL IN YOUR MEMORY
The training of Jack.
He learned archery, horseback riding, dozens of styles of fighting, from masters all over the world.
That right there, is The Warrior that their training created inside Jack. That's the wild animal that he could become, the evil he could be if he took all the skill and knowledge he had, and turned it against the world, instead of Aku.
When Jack see's it, it's him, considering lashing out at the innocent. It's what he's afraid of.