It is well known that Darwin rejected Christianity and the biblical account of creation because of his view of evil. He lost his mother when he was eight years old and his beloved daughter, Annie, when she was only ten. He could not correlate these events with the God of love.
As he developed his ideas on natural selection as a mechanism for evolutionary change, he became aware that this was built on a bitter struggle for survival. Then he was confronted with seemingly awful activities in nature. He mentions the parasitic ichneumon fly that lays its eggs in a caterpillar and, when they hatch, they eat the host.
The final judgment
Ultimately he squirmed at the biblical testimony to the final judgment, which he considered to be a hideous doctrine. Of course, whatever we make of these things, the denial of God does not remove the actuality of these events. They are still there and have to be faced.