Likely answer

Grimdark Fantasy Featuring the Tortured Inquisitor Sand dan Glokta

In Joe Abercrombie's "The Blade Itself," Sand dan Glokta is a former war hero and champion fencer who was captured and brutally tortured for years. Now physically broken and cynical, he has transitioned to a new career as an Inquisitor for the Union, utilizing his dark experiences to extract confessions from others. He is a central protagonist in this gritty first entry of The First Law trilogy.

Confirmed match: The Blade Itself by Joe Abercrombie