In The Godfather Part III, the priest refuses to give Michael Corleone absolution for his sins during the confessional scene because Michael has not truly repented for his actions. This moment is key to the thematic development of the film and Michael's character arc.
The confession scene occurs at the climax of the film, just after Michael’s involvement in the violent retribution against the heads of the other Mafia families has escalated to a point of personal tragedy. Michael is seeking absolution from the priest for the murders he ordered, including his role in the deaths of his enemies, as well as the crimes that have plagued his life as a Mafia boss.
However, the priest refuses to absolve Michael because Michael is not genuinely repentant. To be absolved of sin in Catholicism, one must show contrition and a sincere desire to change one's ways. The priest recognizes that Michael is not remorseful in the way the church requires for absolution—he is still entangled in a life of violence and crime, which prevents him from achieving true spiritual redemption.
The scene underscores Michael's internal struggle and his inability to fully escape the life of crime. Despite his desire for forgiveness, he has not taken the necessary steps to sever ties with the sins that define his existence. His sins are too deeply ingrained in his identity, and as the priest points out, repentance requires a commitment to change—a commitment Michael is still unwilling or unable to make.
This rejection of absolution also reflects the broader theme of The Godfather Part III, where Michael seeks redemption but is constantly thwarted by his past actions and the violence he has perpetrated. The inability to be absolved symbolizes Michael's ongoing moral and spiritual downfall, culminating in his tragic realization that he cannot undo the damage he has caused.