What distinguishes Christianity from other monotheistic religions?

Christianity is the only faith system that recognizes the depth of the problem of sin and offers a solution to it. It is not only the "really bad" people who must be interested in their relationship with God but all of us, since we have all rejected God's authority by sinning. The problem of sin is, once we have done bad instead of good, how can we ever remedy to stand before a perfect and just God?

Islam

Islam recognizes the gravity of sin. The Quran describes God as "quick in calculations" and "severe in retribution". Sinners are eternally punished (5:37. 4:56).
Nell’Islam, the requirements to be at peace with God are to have faith in him and to do good (2: 112, 2:277). Those who don't believe are doomed (3:10, 3:131), how damned are those who worship other gods alongside Allah (4:116), they disobey him (4:14, 4:115) or murder believers (4: 93).

But what happens to believers who do wrong? The Quran describes God as “sometimes merciful, most of the time generous " (3: 31) and they declare that he loves those who do good and will forgive them (3: 148, 152). However, it says that God does not love those who commit sins (2: 276, 3:57, 7:55). Because all people sin during their course of their life, even believers, how can a Muslim be at peace with God – if he loves him for his faith and good deeds, and if the god hates him for his wrongs?

The answer appears to be in 23:102 – 103:

“Those who have heavy scales will have bliss; but those who have light scales, they will be the ones who have lost themselves: will remain in perpetuity "

That is, those who do good will be considered good and their negative behaviors will be forgiven. Forgiveness also requires that the person be sincere and will not have to commit more sin:

Instead, those who feed on usury will resurrect as one who has been touched by Satan. And this is because they say: “Trade is like usury!”. But Allah allowed the trade and forbade it’ usury. Those who desist after the warning of their Lord has reached them, keep what you have for yourself and your case depends on Allah. As for who persists, here are the companions of the Fire. They will remain there forever. (2: 275)

and those who, when they have committed some wrongdoing or have been unjust towards themselves, they remember Allah and ask Him for forgiveness for their sins (and who can forgive sins but Allah?), and they do not consciously persist in evil. (3:135)

O you who believe! Do not kill game if you are in a state of consecration . Which of you will kill her deliberately, redeem himself with some beast of the flock, of the same value as the one he killed – judge two men righteous among you – and it will be an offer that he sends to the Ka'ba, or atonement by feeding the poor or by fasting to pay for the consequences of his action. Allah has forgiven the past, but he will take revenge on repeat offenders. (5:95)

There is also a deadline. Those who repent soon after sinning are forgiven, but not those who repent at the point of death.

Allah welcomes the repentance of those who do evil out of ignorance and who repent shortly afterwards: that's from whom Allah accepts repentance. Allah is wise, wise.
But there is no forgiveness for those who do evil and who, when death presents itself to them, they shout: ” Now I am sorry!”; nor for those who die as unbelievers. For these we have prepared a painful punishment. (4: 17-18)

Can a Muslim be reconciled with God? The first question is whether his good deeds can overcome his sins in quantity. It must be borne in mind that sin includes not only acts which are obviously wrong, but also thoughts of hate, of pride, of lust, of envy, etc.; even those wrongs equivalent in weight to a mustard seed will be considered:

We will set up exact scales, on the Day of Resurrection and no soul will suffer any wrong; even the weight of a mustard grain, we will resurrect it . We will be enough to draw conclusions. (21: 47)

Who can honestly say to do enough good deeds every day to make up for evil deeds?
The Koran says that God will multiply good deeds to compensate for Evil (4: 40); but how can a believer know that he has reached the level of compensation between bad deeds and good deeds?
The Quran says, "He (God) forgives whoever he wants and punishes whoever he wants. " (3:129); it is quite possible that Allah would punish those who think they have been forgiven.

The second problem arises when a person has committed a sin again after repentance, since the Koran clearly states that whoever repeats offenses is not forgiven. We are creatures of habit, after all. If we commit a particular sin once, it is very likely that it will repeat itself later, since sin indicates weakness. Each person has different weaknesses and sins that they are more prone to. There are certain temptations that each of us will have to struggle against throughout our lives. Who can say that these believers will realize God's perfection?
Islam gives the hope of reconciliation with God to believers, but it is only a hope, never a certainty.

Judaism

The Jewish Bible (which is the same as the Protestant Old Testament) it does not explicitly say that one must do this or that to enter Heaven, but it records the Laws and moral orders that God gave to the Israelites. According to Judaism, if God's people obey the laws, will be blessed, but if he disobeys he will be punished (Deuteronomy 11:26-28). It also clearly states the problem of sin: "There is no upright man on earth who does what is right and never sins" (Etc 7:20, also Salmo 14:1-3). It is because of the sin that the sacrificial system it is placed in the Law. however, as the author of Hebrews points out, animal sacrifices are not enough to reconcile us with God:

Jews 8:7-13

Because if that first pact had been without flaw, there would be no need to replace it with a second. 8 Indeed God, blaming the people, dice:
“Here the days come, says the Lord,
that I will conclude with the house of Israel and with the house of Judah,
a new pact;
not like the covenant I made with their fathers
on the day I took them by the hand
to get them out of the land of Egypt;
because they have not persevered in my covenant,
and I, in my turn, I didn't care about them, says the Lord.
This is the covenant I will make with the house of Israel
after those days, says the Lord:
I'll put my laws in their minds,
I will write them on their hearts;
and I will be their God,
and they will be my people.
Nobody will educate their fellow citizen anymore
and no one's brother, saying:
“Know the Lord!”
Because everyone will know me,
from the smallest to the largest of them.
Because I will have mercy on their iniquities
and I will never remember their sins ".
Saying: "A new pact", he declared the former ancient. Now, what becomes ancient and ages is close to disappearing.

With this new pact it has made the first obsolete; and what is obsolete will soon disappear. (Jews 8:7-13, that quotes Geremia 31:31-34)
The priests regularly entered the outer room to continue their ministry. But only the supreme priest entered the inner room and only once a year and never without blood, that he offered for himself and for the sins of the people who had committed them in ignorance. The Holy Spirit was indicating by this that the holiest place still would not be revealed as long as the first tabernacle was still standing..
The law it is only a shadow of good things that are happening – not reality. For this reason it never can, from the same sacrifices repeated endlessly year after year, to make those who take part in this cult perfect. If you could, they wouldn't stop the bidding? If the worshipers felt clean once and for all, they would not have found it necessary to continue making sacrifices. But those sacrifices are an annual reminder of sins, because it is impossible to take away sins with the blood of bulls and goats. (Jews 10:1-4)
That is, if the sacrifices prescribed by the law were enough to reconcile people with God, all observant Jews would have been able to enter the holy place and stand in the presence of God, since their sins would be forgiven. More, if sacrifices were effective they should not be offered perpetually. However instead of being that way, the Jewish Bible itself specifies that the Law and the Covenant must be replaced, since God promises a new covenant with the Israelites.
To conclude, Paolo, makes further clarifications in Galati 3:10-11:

“In fact, all those who rely on the works of the law are under a curse; because it is written: "Damn anyone who doesn't stick to all the things written in the book of the law to put them into practice". And that no one by the law is justified before God is evident, because the just will live by faith "

«Cursed is he who does not abide by the words of this law, to put them into practice!» – And all the people will say: «Amen». (Deuteronomy 27:26).
No one is clearly justified before God by the Law, because, "He is full of pride, does not act righteously; but the righteous will live by his faith. (Abacuc 2:4).

Christianity

How much then does Christianity solve this problem?
The Bible recognizes that we are unable to earn our salvation, since we are too weak and sinful. Only God can help us, offering a perfect sacrifice for our sins: Jesus Christ, son of God. As this perfect sacrifice satisfies the need for sin to be punished, God can offer us complete forgiveness for our sins.

I am therefore under this law: when I want to do good, evil is in me. In fact, I am pleased with the law of God, according to the inner man, but I see another law in my members, that fights against the law of my mind and makes me a prisoner of the law of sin that is in my members. Unhappy me! Who will free me from this body of death? Thanks be given to God through Jesus Christ, our Lord. So then, I with my mind serve the law of God, but with the flesh the law of sin. (Romans 7:21-25)

Indeed it is by grace that you have been saved, by fede; and that not of yourselves:; it is the gift of God. It is not by works, lest any man should boast; (Ephesians 2:8-9)

Indeed, if the blood of goats, of bulls and the ashes of a heifer scattered on those who are defiled, they sanctify them, so as to obtain the purity of the flesh, how much more the blood of Christ, who by the eternal Spirit offered himself clean of all guilt to God, it will purify our conscience from dead works to serve the living God! (Jews 9:13-14).