If God was all-powerful, wouldn't he stop natural disasters?
If God was all-loving, wouldn't he stop suffering?
If God was all-knowing, wouldn't he know that people were going to do something evil and stop them?
Christians may give one or more of the following answers:
God has given people free will. He has shown people how they should obey the Ten Commandments and follow Jesus' life and teaching. It is then up to human beings to decide whether or not to follow God's instructions.
God has a plan for people's lives that they may not always understand. This may include evil and suffering but Christians should trust and have faith in God's plan.
God wants people to follow the example of Jesus and help those who are suffering. God must have a reason for allowing evil and suffering but the reason is beyond human understanding.
Christians also pray for those who suffer and try to help them.
Evil and suffering in this life is a preparation for heaven. Evil and suffering give people a chance to become better people and improve their souls. They believe that God will reward them in heaven.