Nemo contra Deum nisi Deus ipse

"Nemo contra deum nisi deus ipse" means no one can stand against God except God himself. It means that only God has the power to overcome and go against the will of God. Just like if you want to fight against a big bully, only a bigger bully can fight against him. But in this case, the big bully is God and no one can fight against him except God himself. So it's like saying, if you want to go against God, you have to be God yourself, but no one is as powerful as God.