The problem of suffering questions God’s existence with the ample amount of suffering in the world. As Epicurus stated, if God is both omnipotent and omnibenevolent, then there should not be any evil in the first place, since He should both be willing and be able to prevent any evil.
Even though some suffering is the result of humans' own unwise judgement, not all suffering is the result of free will, and much of the suffering is not necessary. And even then, wouldn't any presence whatsoever invalidate the existence of God? As God is the First Cause, why would such an infinitely perfect being be the first cause of evil?
Leibniz attempts to refute this by his doctrine of optimism, yet it requires sacrificing either God’s omnipotence, as God could not eliminate all the evils when creating the world.