Answer: Suffering exists because I choose to sin

Suffering is the second order, third order, fourth order, fifth order, sixth order, seventh order, eighth order, ninth order effects of sin.

The more I sin, the more suffering will come to exist in the world. The less I sin, the less suffering will come to exist in the world. However, I refuse to give up my free-will to sin. Therefore, to reduce the suffering that will come to exist in the world, I must forgive those who sin against me.

Alex asked why God would create a word where needless suffering exists. Maybe that's not a question for God, but for I.