Anselm (c. 1100AD) was undoubtedly the greatest influence on atonement theory since the time of the Church Fathers. An article published in 2008 attempted to honor his contribution (https://www.christianitytoday.com/2008/08/anselm/). However, the question never really addressed in that article was whether his contribution was an advancement of atonement theory, or a terrible distortion.
In the feudal system of his day, serfs who offended their lord were bound to be punished unless they were able to offer some form of satisfaction acceptable to the lord, who would then release the serf from the penalty. Drawing an analogy from that practice, Anselm came up with what we now call the “Satisfaction Theory of Atonement.” His thesis was that humanity had deeply offended God through sin, and that unless sufficient satisfaction could be made, humanity must be punished. Unfortunately, no human could make sufficient satisfaction; and that is why Jesus came: to provide the necessary satisfaction to save mankind.
The most obvious problem with his theory is that he did not get it from Scripture; he drew an analogy from the feudal system of his day. Given that this was part of the depraved culture of that era, it can hardly be the starting point for reliable theology.
But far more serious is the total inversion of our understanding of atonement that came with his theory. Whereas the prior Ransom Theory had tried to explain how the cross was the means for rescuing humanity from the power of Satan, Satisfaction Theory stood that idea on its head by declaring that the cross rescued us from the jaws of justice, demanded by God Himself. A few hundred years later, this gave birth to the now commonly accepted Theory of Penal Substitution, an even more legal-centric theory of atonement.
While a full critique of this disaster is beyond the scope of a small article, the truth is that this distortion of atonement has been one of the worst theological errors in history. Ideas have consequences! Among other things, it completely destroys the Biblical concept of forgiveness. But worst of all, this theory has distorted the entire rescue operation of God and laid the foundations for a gospel concerned only with the afterlife, and has no direct relationship to discipleship or an ongoing life with God today. It is why so many people now believe that one can be a Christian your entire life without ever becoming a disciple of Jesus.
Anselm may have been a brilliant man. He may also have been a very good man. But his theory of atonement came from the Father of Lies!
For a better understanding of how amazing the atonement truly is, and how it is the foundation for a gospel of the exchanged life, see Lamb of God.