Even though the True God didn't believe Zhou Tian could defeat him without using the rules, given that the battle concerned his life, the True God dared not underestimate him.
If Zhou Tian had lost, it wouldn't have been a big deal for him. At that time, if Zhou Tian used his rule abilities, the True God knew he had no power to harm Zhou Tian. Even if he suffered losses at the hands of Zhou Tian, he would have to accept it then.
But the situation was different for the True God. Although he didn't know what Zhou Tian was planning, he was very clear in his heart. Considering the situation at the time, if Zhou Tian indeed had such intentions, he was entirely capable of killing him.
Thus, for Zhou Tian, perhaps that battle was just a Game. But for the True God, it was absolutely a life-and-death battle. If he lost to Zhou Tian, then Zhou Tian could kill him if he wished, and even if Zhou Tian spared him, the True God wouldn't fare well.
