First of all, it’s a really deep question, and you’re not alone in wondering about it. There always seems to be more evil in this world than we can comprehend. We read about God’s great justice, hear reassurance that all debts will be cleared, and that the evil will suffer eternal punishment, but it just seems abstract. Here are a few verses to clarify those thoughts:
“For God shall bring every work into judgment, with every secret thing, whether it be good, or whether it be evil.” Ecclesiastes 12:14
“But why dost thou judge thy brother? or why dost thou set at nought thy brother? for we shall all stand before the judgment seat of Christ. For it is written, As I live, saith the Lord, every knee shall bow to me, and every tongue shall confess to God. So then every one of us shall give account of himself to God.”
“For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad.”
2 Corinthians 5:10
Most assuredly we can be sure that whatever debt is owed to us shall be paid in full.
The one thing we must remember is who is actually wronged in these scenarios we look at. Yes, we humans are often unjustly treated by other humans, perhaps we do not deserve to be treated so harshly in a situation, or to be persecuted for beliefs, etc. but before we look at the human who has been wronged we must look at how God has been wronged. One tiny sin is enough to damn us to hell for eternity, and without the saving grace of Jesus, that is exactly where we’d all be headed. So we should not compare the number of sins, or the number lives taken, or how bad one sin is in comparison to another, each sin is as devastating to the perfect holiness of God as any other sin.
So when justice is to be served, we can be sure that the perfect and holy judge, who has been seriously offended by each sin committed by every single person on the planet, will exact the correct amount of punishment to reconcile every life lost, every lie ever told.
Everything that is done in darkness shall be brought to light. Luke 8:17.
God knows everything that each of us has ever done. The difference is whether or not he sees the ransom paid for our lives, is paid in full. If there is no surety for our debt of grievous error and evil, then we have no way to ever hope to pay it back. No amount of good things we can do will ever balance our scales. And when the evil are banished to Hell, they will experience something they have never experienced before. Because God’s common graces abound to all people, even those who do not believe. They have general goodness in their lives. They may have happy marriages, or wealth, or health, or anything we consider earthly goodness. But for the first time in their entire lives they will feel the full removal of God’s graces. They will feel the complete absence of light, and joy and hope, and love for all eternity. They will be crushed under the weight of guilt and torment and darkness unlike any other blackness. They will feel the anguish of all they have done, and each time they rejected the Lord. It will be their constant companion for the rest of eternity. Can you imagine anything worse? The souls that were wronged in this life will have their own account to give and they will suffer according to their sins, or they will be saved by the blood of Jesus Christ. And I do believe that the children of God will have no reason to be concerned about the debts anyone owes them. They will have eternity in heaven which makes up for everything in much more completeness than any apology from another human. We will be filled with the fullness of Jesus Christ in perfection, and being perfectly healed and justified, we will care no more.
In the end, the amount of suffering unbelievers experience will be proportionate to the evils they’ve done, I do believe. So I’m certain Hitler, Stalin, Mao, Pol Pot, and the like will pay for every debt they have in the fullness of time.
In the same way we can store up treasure and riches in Heaven, the evil bring the wrath of God upon their heads with greater and greater fury.
I hope that helps you out a bit. His blessings on you!
Grace and Peace to you,