Evil is obviously present in the world, seen in murder, child abuse, terrorism, and natural disasters. Many Christians and non-Christians don't understand why evil is present in the world. What's important for Christians to remember is:
None of this was originally supposed to happen.
God created the world ‘good’— everything that was created God considered “good,” and that word actually means ‘perfect’ (Genesis 1:102; 31). The world was a world of goodness, harmony, vitality, hope– even ‘bliss,’
In Genesis 3, we read of the Fall. Adam and Eve were innocent, not perfect, and The Fall was a volitional, willful, deliberate act of Adam and Eve to break God’s command– and to do that which was forbidden. Giving in to temptation, they rationalized their desires, justified their behavior in their own eyes, and did what they wanted to do. The Fall occurred as a result... it set into motion ruin, spoil, contamination, corruption— and every human evil and disposition that there is. Each is cursed for playing a role in what happened (Genesis 3:16ff)
The effects of the Fall were: a broken relationship between God and humanity, strained relationships between human beings, and the injection of evil into the world. This caused disorder, loneliness, heart disease, physical problems, pain, aging, death, corruption.. Entered the cosmos (the world God created and everything in it)
The Fall Resulted in The Curse... which unleashed EVIL on a cosmic/global and a personal scale. The sin of Adam was like turning a lock and opening the door for the spoiling of the universe and all humanity.
Evil had three expressions: bad things or evil as a direct consequence of deliberate human choice (making a decision to do something bad– killing someone), as an indirect consequence of non-deliberate human choice (unintentional killings and lesser situations; things going wrong even though people didn’t mean to do things wrong), and bad things ‘just going wrong’ without any humans being involved (natural disasters).
All of these things are effects/consequences of the Fall or “Expressions of the Curse”
Jesus came to address the problem of Evil. He did so by attacking and defeating ‘sin.’ He did this through giving his life on a hill called Calvary on the cross of crucifixion. When He did that, he won the war, but now all things must unfold to that great end of the age— as He continues to work out His plan on earth. The Bible (end of time/beginning of eternity) ends with the destruction of the Curse— and the resolution of all human pain and suffering forever– UNDOING THE EFFECTS OF SIN.
God does not introduce evil into the world, it entered through the Fall, through our sin. When Jesus returns, the effects of sin will finally end. God will come to judge and to undo the effects of sin.