[Ali Imran]

So you believe every human is born with a clean slate and that your God is a forgiving one. The laws of Allah are there to guide adherents, but if they stumble and fall, they have a Celestial being who has the magnanimity to forgive them, so they can wipe the slate clean and start afresh.

By contrast, Christianity teaches that humanity's problem is much more severe. All people are born in a corrupt state and are held responsible for being in that corrupt state. We have inherited a defective "internal operating system" that alienates us from God. No efforts to eradicate or rehabilitate humanity's rebellious nature that is opposed to God will succeed. As the apostle Paul wrote, "All have sinned and fall short of the glory of God" (Rom 3:23).

We face the problem of immunity to holiness by virtue of our camaraderie with sin. Everyone gets tainted by sin but remains free to act according to his disposition. Because the disposition is corrupt, man lacks the moral ability to obey God. Only by grace can such a fallen creature be restored and redeemed. Without that grace, efforts of moral perfection are doomed to failure.

God never owes us grace. And grace is not justice. If God deals with us ultimately on the basis of justice alone, we will perish. Contrary to what you think, God is both forgiving and just. His righteousness demands that He punish sin, but His love motivates Him to offer a way to forgive sinners.

The question remains unanswered: where did evil begin to exist

All the prophets taught the same, to repent and seek God's forgiveness. The only odd one is Paul, who came up with unheard-of ideas. 

It is not justice to punish an innocent man (Jesus) for the wrongdoing of others (people). 

When you demand payment for a wrong done to you, that means you did not forgive. If Bob owes me money and I made my son pay me what Bob owes, that is not forgiveness. It is as simple as that. I don't know how Christians missed that.

And remember, Ezekiel taught that if we repent and seek God's forgiveness, our sins will be erased. Why would you criticize that when it is in your Bible?

Humans can do evil because God created us with the free will to do evil, or good. Let's not create a problem when there is none. Paul did exactly that, creating a non-existence problem.