In Don Carson’s book Love in Hard Places (pages 76-77), he writes this:
“Who has the right to forgive the offenses of another? This side of the Holocaust, the question has been raised in plaintive terms. Only the victims of the Holocaust have the right to forgive the perpetrators, argues Simon Wiesenthal; and since they are all dead, no forgiveness is possible. It is not merely impertinent for others to think they can forgive such crimes; it is immoral, odious. How would the victim of a vicious rape feel if I went up to the perpetrator and declared that I forgave him? Would she not scream out that I do not have the right?
That is why, in the ultimate sense, only God has the right to forgive sins, all sins-for all sins have first and foremost been committed against him, as David himself recognized (Ps. 51:4). This is not to deny that many others may be abused, violated, offended; it is to say that in the ultimate sense, what gives sin its deepest odium, its most heinous hue, is that it offends the God who made us and who stands as our Judge. That is why he and he alone has this ultimate right to forgive sins.”
All humanity will have to stand before God and account for their lives. While we may have to ask others for forgiveness when we sin against them, we will always have to ask God for forgiveness for any sin, even one where no other person is hurt.