Something dawned me today.
Isn't it wonderful when the Holy Spirit brings something new of God to our attention?
If someone committed murder and let's say you get a life sentence in prison but you repented truthfully in your heart and accepted Jesus as Lord and Savior, then I assume God would forgive that person even though they will still live out their natural life behind bars. But when they die, they will go to heaven. (Imagine how the victims' family must feel if they knew even though this person will spend rest of their life behind bars, they will get a great reward when they enter the afterlife in heaven --> the only way for that family to proceed is to truly forgive the murderer otherwise they will always feel injustice was done to them and the person should never get to enter heaven).
Yes. This is one of the reasons that Jesus stated that without us forgiving others there is no forgiveness for us (Matthew 6:14-15).
But what if that person is responsible for the murder of 1 million people? Obviously that person didn't physically murder each of the million persons with their bare hands, but let's say that person was a leader of a country and ordered the nuclear strike on an enemy state and it resulted in the deaths of 1 million people. Now let's say that leader one day truthfully repents to Jesus and accepts Jesus as LORD and Savior....will God still forgive them?
The short answer is yes. As long as the person truly repents of their unbelief and receives Jesus as Lord and Savior, all sins are washed away and they become a new creation in Christ.
Is there a limit to which how many people you murdered there's a point of no return?
In theory, no. In reality, though, we must acknowledge that such actions take their toll on the conscience and heart of the person who kills repeatedly, and there may be a point that such a person will have damaged themselves so badly that they would never be able to believe. Still, no one knows the heart and conscience but God alone, so I don't think we can place a number on the limit as fallible human beings. For example, no one knows for sure, but it was reported that the serial killer Jeffrey Dalmer came to Christ while in prison, and he performed some of the most heinous acts imaginable. There is a good chance that Dalmer will be in heaven, though.
If God does forgive that leader and when that leader passes away behind bars or execution, he will go to heaven. Imagine how many people on earth would disagree with God on that decision and they themselves might be Christian too. Imagine all the families and friends of the victims....so everyone would have to find it in their hearts somehow to forgive this person otherwise they will always live in resentment and bitterness towards God for letting him into heaven?
Grace is always extended to the undeserving, otherwise it is not grace (unmerited favor) but their due (earned by works). It is only when we realize our own depths of depravity that it becomes more likely for us to find forgiving others easier. Perhaps this is why some of the most powerfully used people in history have been those who committed terrible sin in their pre-Christ days (Paul is the prime example). That said, in eternity we will know fully (1stCorinthians 13:12) just as we are fully known, and all our doubts, questions, and unbelief will be washed away.
I fee compelled to add that there is unforgivable sin. Jesus said as much:
Then one was brought to Him who was demon-possessed, blind and mute; and He healed him, so that the blind and mute man both spoke and saw. And all the multitudes were amazed and said, "Could this be the Son of David?" Now when the Pharisees heard it they said, "This fellow does not cast out demons except by Beelzebub, the ruler of the demons." But Jesus knew their thoughts, and said to them: "Every kingdom divided against itself is brought to desolation, and every city or house divided against itself will not stand. If Satan casts out Satan, he is divided against himself. How then will his kingdom stand? And if I cast out demons by Beelzebub, by whom do your sons cast them out? Therefore they shall be your judges. But if I cast out demons by the Spirit of God, surely the kingdom of God has come upon you. Or how can one enter a strong man's house and plunder his goods, unless he first binds the strong man? And then he will plunder his house. He who is not with Me is against Me, and he who does not gather with Me scatters abroad. "Therefore I say to you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven men. Anyone who speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age or in the age to come. "Either make the tree good and its fruit good, or else make the tree bad and its fruit bad; for a tree is known by its fruit. Brood of vipers! How can you, being evil, speak good things? For out of the abundance of the heart the mouth speaks. A good man out of the good treasure of his heart brings forth good things, and an evil man out of the evil treasure brings forth evil things. But I say to you that for every idle word men may speak, they will give account of it in the day of judgment. For by your words you will be justified, and by your words you will be condemned." (Matthew 12:22-37)
In this passage, the Pharisees attributed the work of the Holy Spirit through Jesus as being the works of the devil. Jesus says this is an unforgivable sin. If one persists in this belief, there is no way for them to place their faith in Jesus.
Here is the other side of the same coin:
And another angel followed, saying, "Babylon is fallen, is fallen, that great city, because she has made all nations drink of the wine of the wrath of her fornication." Then a third angel followed them, saying with a loud voice, "If anyone worships the beast and his image, and receives his mark on his forehead or on his hand, he himself shall also drink of the wine of the wrath of God, which is poured out full strength into the cup of His indignation. He shall be tormented with fire and brimstone in the presence of the holy angels and in the presence of the Lamb. And the smoke of their torment ascends forever and ever; and they have no rest day or night, who worship the beast and his image, and whoever receives the mark of his name." Here is the patience of the saints; here are those who keep the commandments of God and the faith of Jesus. (Revelation 14:8-12)
Everyone who believes that the Antichrist and false prophet are doing their works through God will also have committed an unforgivable sin. So we see that attributing the works of God to Satan and attributing the works of Satan to God are unforgivable sins. If one persists in these beliefs, they would never come to saving faith in Jesus as the true Lord and Savior.
Hope this helps.