I think the existence of evil in the world does more to prove God’s existence than to disprove it (see this for more on that idea).
Some consider the existence of evil as proof that a loving God doesn’t exist. But while such philosophical discussions are important, there is an element of silliness to it. If I created a model universe with all the complexity of ours, and one of my little sentient creatures on my model earth determined that since he couldn’t fully understand everything about me and the universe I created and concluded that I must not exist – even after I wrote my moral code on their hearts and clearly revealed myself to them- I would find it amusing and irritating.
The end of the book of Job is there for a reason (as well as other passages).
Job 42:1-6 Then Job replied to the Lord: “I know that you can do all things; no plan of yours can be thwarted. You asked, ‘Who is this that obscures my counsel without knowledge?’ Surely I spoke of things I did not understand, things too wonderful for me to know. “You said, ‘Listen now, and I will speak; I will question you, and you shall answer me.’ My ears had heard of you but now my eyes have seen you. Therefore I despise myself and repent in dust and ashes.”
The question of evil is typically offered as a challenge to Christians, as if it is only a problem for us to explain. But how does the atheist explain it? It is an even more difficult question for them to answer. They can’t provide a foundation for the morality that they constantly reference. There is no redemption of evil in their worldview. That isn’t what makes their view wrong, of course, it just shows how the problem of evil isn’t the trump card against Christianity that many make it to be.
God permits evil, restrains evil and will ultimately redeem evil. He already defeated sin and death at the cross.
Here are some terrific YouTube videos on the issue of evil.