The Quran says: "for who but God can forgive sins?" (3:135)
In other words, who other than God can delete my sins from the record of my deeds?
The above verse speaks about what we refer to as "deleting something". A person's deeds have unlimited items. Deleting those deeds which are unwanted can be done only by God. God alone can delete undesired aspects from our record of deeds. 
Another verse says: Copy Arabic text. When I read the Quran, I find this verse to be the greatest mercy for a person. It means: "O My servants, who have committed excesses against their own souls, do not despair of God's mercy, for God surely forgives all sins." (39:53) There is nothing exempted from this. 
The Islamic concept is that if a person repents sincerely, he will be forgiven. All his past sins will be deleted. A person has been given the chance to repent to the final moment. A hadith tells us: "A person has been given a chance to repent till the end of life." (Musnad Ahmad 6160)  In Islam the concept of forgiveness is very vast, there is nothing exempted from it.