"Justice : attacks only if your HP is less than the opponent
at the beginning of your turn."
Seems relatively balanced. However, is "Justice" really an attribute? Would it be a future one in the game?
exempli gratia: You know how sometimes when a card in the game is about to run out of text, they say a status name like "Immaterial"? We know what the status "immaterial" does. But would this "justice" term be used in the future if you know what I'm saying.
So instead, I personally think it should write "This creature only attacks when your HP is less than the opponent's at the start of your turn."
Also, the upped one could be called "Templar of Justice", just saying. I think it is more apt than "Hero of Justice".