"...the redemption of a man who made a single mistake decades ago by a man who spent decades making up for the mistakes of others." "a man who made a single mistake decades ago" Let's call this person "Man A". Man A committed a crime decades ago and has been in prison for it. It appears, from the word "mistake", that the crime was not murder or rape, but rather something like drug use or a money scheme. "a man who spent decades making up for the mistakes of others" Let's call this "Man B". Man B was found guilty of a crime he did not do. He has spent decades in prison, but it was for someone else's crime ("the mistakes of others") -- not for his own crimes. It seems Man B helped Man A get out of jail or have a better life after jail (possible along with Man B himself escaping). If this is in regard to Stephen King's book, "The Shawshank Redemption", then I believe this is correct. In the movie version, Man B was played by Tim Robbins, and Man A was played by Morgan Freeman.

First of all, I must say that this sentence is poorly constructed. I myself had to read it over a few times before I completely understood what this person was trying to say, and I was only able to understand because I have seen the film (The Shawshank Redemption). It looks like this paragraph has been taken from a review of the film/book "The Shawshank Redemption." In order to explain the meaning of the sentence you asked about, I would have to reveal some of the plot of the film, so if you have not seen it yet, you may not want to read any further. The most important part of understanding this sentence, is understanding the meaning of "redemption", so that is where I will start. As a theological concept redemption is an element of salvation that broadly means the deliverance from sin. The English word redemption means 'repurchase' or 'buy back', and in the Old Testament referred to the ransom of slaves (Exodus 21:8). In the New Testament redemption is used to refer both to deliverance from sin and freedom from captivity. Taken in its widest sense, redemption is release from guilt, obligation, or punishment. Now back to the sentence in question: "...the redemption of a man who made a single mistake decades ago by a man who spent decades making up for the mistakes of others." The author of this quotation is talking about the two main characters in the film: "Andy Dufresne" and "Red". The man who made a single mistake decades ago is "Red." He committed a crime many years ago, and spent over thirty years in prison paying for his "mistake." The man who spent decades making up for the mistakes of others is "Andy." Andy was sent to prison for murdering his wife, but he was wrongly convicted - he was innocent. So what the author is trying to say is that "Red" received redemption from "Andy".