God supposedly has made all things from nothing. He is loving and good but yet there is so much wrong in creation. The idea is that he gave us free will and we distorted his creation by abusing it instead using it to create a world of love.
Christians say God does not make evil. Evil is a mere lack of a good that should be there.
For human evil though, evil is a lack yes - but the human takes good and twists it.
There is no free will then to choose or make evil other than a lack or a distortion.
The lack doctrine seems confused - evil is hardly that bad if it is a gap. And the distortion doctrine says we put good in the wrong direction - it denies that moral corruption happens.
Nobody sees this lack - it is only thinkers talk about it. Nobody offers any empirical or logical proof of the lack. We do see good being distorted but that does not mean there is a lack.
The believer has to admit that his idea of free will and its place in God's plan is unconvincing. And it is incoherent.
APPENDIX: ILLUSION
The problem of evil is how God can be called love and allow terrible things to happen to innocent people.
Some argue that the notion of evil being mainly or essentially a lie or unreal - or an illusion solves it.
This shifts the problem of evil to a new problem. And a worse one. God ends up being accused of creating the illusion of suffering and sickness and injustice and hate.
It is argued that:
The proof that God did not create evil is that there is no completely evil being or thing
The reason is that making one is impossible.
This gives rise to the eccentric notion that a wholly evil being would be the same as a non-existent one. So turning totally evil is impossible for all that will happen is that you would vanish permanently out of existence. So Hitler's twin brother was so evil that he never came into existence?
What happens to a totally evil sin or crime? Religion is forced to admit it has enough good in it and is mainly good which is why it exists!