As people who know me well know, one of my all-time favourite stories is Les Miserables.
One of the many great elements about it is the relationship between Jean Valjean and Javert, which explores the tension between law and grace.
Javert is an implacable policeman, who knows Valjean from prison before the story starts. Valjean is a paroled hardened convict, who is transformed by an encounter with grace in probably the most famous scene in the book, which I might discuss some other time. Javert finds out that Valjean has broken his parole, and vows to hunt him down.
A large part of the book is Valjean hiding from Javert, escaping from Javert, handing himself in to Javert, and so on. Eventually, they find themselves on the same side of a barricade in the Revolution of 1830. Javert is an undercover agent working against the rebels; Valjean is trying to save the life of one of them.
Javert's identity is discovered, and Valjean volunteers for the job of executing him, but then lets him escape. Javert goes away, his whole system of values destroyed by the fact he owes his life to a convicted criminal. There is no place in his mind for grace or change. So when he again captures Valjean, he does not know what to do. Either he frees the man to whom he owes his life, making himself into a criminal, or he hands him over to the galleys, which makes him incredibly ungrateful.
Javert sees no option for himself but suicide - grace not just triumphing over law, but destroying it utterly.