This is a matter about which very wide differences of opinion are evident. Some have believed that this is an evil reality, dominated by evil; others see the powers are equally balanced over the long term.
Mainstream 'Classical' Christian theology is at one extreme; positing an omnipotent and wholly-good God creating that everything from nothing. This suggests that ultimately there is no evil; evil is a temporary aberration - or a matter of deceptive appearances. Evil cannot win.
From my own perspective; I see God as a creator Being (indeed as Heavenly Parents); and creation as a developing, ongoing 'project' in a universe of chaos. Evil is regarded as opposition to creation, the destruction of creation: in essence opposition to God's project of creation.
And men are regarded as children of God - as pre-existing eternal Beings who have been procreated and thereby transformed to be more-like God, which includes greater free-will or agency via higher consciousness, greater awareness.
So, evil is a genuine possibility; but ultimate evil entails self-destruction because each Being is himself a product of God's creation. So opposition to God is aiming-at destruction of one's own consciousness, and destruction of that of oneself that was created by God. The overall aim would be a restoration of creation to universal chaos, including (if possible) the destruction of God's capacity or will to create.
I understand Heaven to be God's way of placing creation beyond the power of evil; since the process of Man's voluntary resurrection to eternal incarnation places Men beyond the power of evil; and places Heaven itself beyond the influence of evil.