I can tell you have a lot of thoughts on this issue, and I saw on your other post on Connect that this is a personal issue for a lot of people that you know. I may not be able to answer all your questions, but I’ll do my best to address some of the things you said and what I think the overarching issue is.
You said “I’m more inclined on the matter of crime not the thought and heart sin but really criminal activities.” The thing is, our actions flow from our hearts and thoughts. They’re a reflection of who we are inside. In Matthew 15:19, Jesus said “For from the heart come evil thoughts, murder, adultery, all sexual immorality, theft, lying, and slander.” We cannot separate our actions from the state of our hearts. So the question isn’t “Can someone do this thing and be forgiven?”, but “Has this person been born again?”
As I said before, someone living a lifestyle of unrepentant sin is showing that they haven’t been transformed by the Holy Spirit. So your examples of people who are involved in crime and claim to be Christians, or those who even claim to represent Jesus as priests and yet are committing abuse, are showing that their hearts are unrepentant to the Lordship of Christ. In Matthew 7:21 Jesus says “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but the one who does the will of my Father in heaven. On that day many will say to me, ‘Lord, Lord, did we not prophecy in your name, and cast out demons in your name, and do many mighty works in your name?’ And then will I declare to them, I never knew you; depart from me, you workers of lawlessness.” In this passage we see that a saving relationship with Jesus involves both knowing and obeying him. They are tied together. In John 14:15 Jesus said, “If you love me, you will keep my commandments.”
This kind of love and obedience cannot be achieved through mere moral effort. We need the Holy Spirit to empower us. John 3:3 states, “Jesus answered him, ‘Truly, truly I say to you, unless one is born again he cannot see the kingdom of God.’” This happens when we give our lives to Christ—our whole lives—and we acknowledge him as Lord. If he is truly Lord of our lives, it follows that we are obeying him as our master.
You said “One man’s heart can change from pure to evil and evil to pure at almost anytime when environment and temptation come or when repentance and forgiveness is available. For someone who is living at such borderland the doctrine “Once Saved Always Saved” is a ticket for them to continue living in the criminal life until such life is almost expire and repent to gain salvation again or salvation was never lost as repentance and forgiveness is just act to lessen the burden of the sinful heart.” Paul addresses this kind of “free ticket” attitude toward sin in Romans 6:15 when he says, “What then? Are we to sin because we are not under law but under grace? By no means! Do you not know that if you present yourselves to anyone as obedient slaves, you are slaves of the one whom you obey, either of sin, which leads to death, or of obedience, which leads to righteousness?”
Someone can’t follow God and keep living in habitual sin. We cannot serve two masters (Matthew 6:24). Someone who claims the name of Christ and lives in unrepentant sin is showing their true master.
However, the Bible is clear that all people can be forgiven, even people who have committed unthinkable crimes. Paul, who persecuted the church, oversaw the murder of Stephen, and described himself as the worst of sinners, was forgiven completely and became a blessing to the church. Even the thief on the cross acknowledges himself as a sinner, recognizes Jesus’ identity, and asks to be remembered, and he is forgiven. This is the glory of the gospel message: all of us deserve judgment and punishment, and yet because of Jesus’ substitute and sacrifice we’re offered forgiveness and salvation. But we can’t get this on our terms, living our way. We must repent.
If you’d like to hear a first-hand account from someone who has dealt with God’s forgiveness for unlovable people, check out this interview from the most recent RZIM Ask Away podcast:
Beyond that, I’d really encourage you to meditate on the book of 1 John. I think it has a lot to say about the questions you’re asking, and I think the Lord could use it to speak to you in a deep way.