Evil is that which is morally wrong or sinful, since God is good and the measure of goodness, evil is essentially that which goes against His nature and His ways. Evil exists in our world because some of God’s creatures rebelled and continue to rebel against Him.
At creation, God saw that everything He made was perfect, but by Satan and his angels, evil came into the world. This rebellion of God’s creatures brought so much evil even unto this day, every generation outperforming the last.
Satan and one third of angels in heaven were involved in this rebellion against God, for this reason, they were thrown down from heaven.
Ezekiel 28: 15;
Thou wast perfect in thy ways from the day that thou wast created, till iniquity was found in thee.
and Isaiah 14: 12 expounds on this.
How you have fallen from heaven, morning star, son of the dawn! You have been cast down to the earth, you who once laid low the nations!
Apparently, this represents the actual beginning of evil in the universe, followed by the fall of Man. Sin originated in the free will of Satan when he chose to rebel against the Creator. Then Eve fell into his trap of deception in the Garden of Eden, Adam followed suit and then there was Cain who killed his brother, and then evil started spreading. The Bible makes us to understand that the inclination of the thought of man is constantly evil. In the present times, the people killing, destroying and carrying out various criminal acts are humans who choose to become evil by their own free will. As the population of the earth increases, evil grows, but thank God for God’s perfect plan of salvation, through it he rescued us from all evil.
Evil persists because mankind has a sinful nature and because God is loving and patient, He wills everyone to be redeemed through repentance, that none should be destroyed.
Satan’s influence is very strong especially for as many as are blinded by him and so evil will persist until Christ’s second coming. Christians should not be overcome by it but should overcome evil with good.
Romans 12:21
Do not be overcome by evil, but overcome evil with good.
I am 
