The Christian God forgives His followers because of the sacrifice of the son. Why is it said of yours that he will not forgive even if you ask 70 times?

Praise be to Allah, the Lord of the World; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Christians claimed that the Lord became angry and punished Adam (Alaihi as-Salam) when the latter ate from the tree. They also believed that punishment became general and embraced the progeny of Adam (Alaihi as-Salam) till Jesus' (Alaihi as-Salam) advent and crucifixion, and that progeny was in the prison of Ibliss (The Devil). So, the dead of that progeny were to go to The Hell-Fire in that prison. In addition, they (the Christians) stated that even Prophets, like Noah, Ibrahim, Moses, Dawood and Sulaiman (Alaihi as-Salam) faced the same fate, but Jesus became their Savior at the end. Here is the statement of this claim in detail:
According to the Christian belief, Jesus, both in his human and divine nature, enabled disbelievers to crucify him so that he could punish Ibliss. They (Christians) said that Jesus concealed himself to prevent Ibliss from recognizing him. They also believed that Jesus enabled his enemies to take him by force, to hit him, to spit in his face, to put thorns on his head, and then, to crucify him. So, he showed sadness saying: "O My God! Why have you invested my enemies with authority over me?!" Then, he disappeared. But, Ibliss could not recognize if that happened to God or to His Son. And Ibliss wanted to take Jesus to the Hell-Fire as he had done with the spirits of Noah, Ibrahim, Moses and other Prophets, and pious men. Here, The Lord said: "What made it permissible for me to die?" Ibliss said: "Your Sin". So, Jesus said: "I did not commit a sin, since my human nature is not like the human nature of Prophets, who committed sins for which their souls were sent to the Hell-Fire! They (the Christians) added: 'Thus, it became legal for the Lord to punish Ibliss and to free the progeny of Adam from being sent to the Hell-Fire!'
That is the wrong belief of the Christians. It is a great insult and abuse against God The Almighty. In fact, nobody ever blasphemed the way that the Christians did. How could any sensible person believe that Allah, The Almighty, punished the progeny of Adam for a sin that their father committed and repented from and that Allah forgave him?
Was it possible that Allah enabled Ibliss to throw the souls of the Prophets in the Hell-Fire as well as to save those of disbelivers and the arrogant who came after Jesus? How could sane, intelligent people accept that Jesus was crucified and then it is Ibliss who was punished? Was it not possible that Ibliss said: "O my God! I did not know that it was You or Your Son. I thought that it was one of Adam's progeny. So, I had a genuine excuse".
Why delay Ibliss' punishment till the advent of Jesus? Did Allah endorse Ibliss' deeds or was He unable to punish Ibliss? Far is He above what they ascribe to Him!
In brief, this belief contradicts sound mind and true faith in Allah, The Almighty. So, how can it be said that God of the Christians forgives their sins due to His Son's ransom (crucifixion)?
In addition, they do not believe that their sins are to be forgiven by Jesus' crucifixion. But their priest and clergymen ask sinners to confess their sins before them. This practice, in turn, causes distress and hardship to sinners and then drives priests to immoral behaviour and indecent scandals.
Islam rejects any mediator between the Creator and His creatures. A Muslim can repent for himself simply by faithful return to Allah and asking His forgiveness from the depth of his heart. Allah asks His servants to conceal their sins from being known to others.
Allah Says (interpretation of meaning): {And when My slaves ask you (O Muhammad) concerning Me, then (answer them) I am indeed near (to them by My Knowledge. I respond to the supplicant when he calls on Me.}[2:186].
As for Allah's statement {Whether you (O Muhammad) ask forgiveness for them (hypocrites) or ask not forgiveness for them (and even) if you ask seventy times for their forgiveness… Allah will not forgive them, because they have disbelieved in Allah and His Messenger….} [9:80]. This verse is special for those who breathe their last as non-Muslims. But, one who dies professing Islam or seeking Allah's forgiveness before his death, Allah has promised in the sacred Hadith: "Seek My forgiveness, and I will forgive You". Yet if a disbeliever returns to Allah and repents before his death, Allah will forgive his previous sins. In the Qur'an: {Say to those who have disbelieved, if they cease (from disbelief) their past will be forgiven…}[8:38].
Allah knows best.