The question of can God create a being more powerful than himself is a question that is a part of the omnipotence paradox. The omnipotence paradox is a series of questions/challenges that try to challenge the notion that God is omnipotent (all-powerful).

So to answer the question, no, God cannot create a being more powerful than Himself. This is not the only thing that God cannot do. With the omnipotence paradox, it’s often asked if God can do the logically impossible, like create a married bachelor. He cannot create a married bachelor because a married bachelor is an illogical concept. God cannot do the logically impossible. Being illogical is at contradiction with God’s nature, so God cannot do the logically impossible.

At the heart of the omnipotence paradox is a misunderstanding about what it means for God to be all-powerful. When Christians say God is all-powerful, they are saying that God can do all possible things.

So looking specifically at the question of can God create a being more powerful than Himself, the first thing we have to realize is that God is not a created being. God created everything else, no one created God. Even if God could create a being that was more powerful than himself, that being would still be contingent, because it was created. So how could a contingent being be more powerful than a non-contingent, eternal Being? It couldn’t. 

Additionally, we have to realize that God is already all-powerful. God can already do all possible things, so there is no conceivable being that could be greater than God.

So no, God cannot create a being more powerful than himself, but that does not change God still being all-powerful.