What is the objection from the problem of evil to the existence of God?

The problem of evil attacks the principle that God is an omniscient, benevolent and omnipotent being. If God were omniscient, he would know that evil exists and he would know how to prevent it. A frequent objection is that a world in which evil exists is necessary, however if God were omniscient, he would know of a world in which evil doesn't exist. Furthermore, if God were benevolent, he would want this world, as he would not want any evil to exist. Finally, if God were omnipotent, he would be able to create a world without evil in it. So, we have seen that if God were omniscient, omnipotent and benevolent, he would know how to create a world without evil, would be able to create a world without evil, and would want to create a world without evil. However, evil does exist in the world. Therefore, an omniscient, omnipotent and benevolent God cannot exist.