Everything is good to the degree to which it conforms to God, and everything is evil to the degree to which it does not conform to God.
No attribute of God conflicts with any other attribute of God. He is as good and just when He rewards good as He is good and just when He recompenses evil with justice.
If God is just, and the message of His severity against sin and His punishing of the guilty is clear, how then is the Christian message that God is justifying the unjust?
The only answer is Mercy. God, in His divine mercy, decided to die on the cross for us.
Listen to this message and learn about the Justice of God.