To understand evil, one must first understand God.
God Himself is good. (Psalm 11:7)
God created a world that fell due to man's sin. (Romans 5:12)
God will recreate the world - without evil. (Revelation 21:1)
God is stronger than evil. (Matthew 13:41-43 & Revelation 19:11-21)
God controls evil and helps us overcome it. (Matthew 11:28-30)
God uses everything for His good purposes. (Genesis 50:23 & Romans 8:28)
When we are blinded by envy or hatred (forms of evil), it is impossible to see our own sin.