Break Him
A mission gone horribly, horribly wrong: Forced to leave a member behind in the hands of some kind of dark guild, Lucy and Happy frantically rush to Fairy Tail for backup. A plan of action is formed, but it's slowly falling apart. Caught up in a slave trade and at the mercy of a man whose namesake is a damn potato, Natsu has a hard lesson to learn: sometimes rushing into things without thinking can have dire consequences. "The human body can bear immeasurable pain and yet recover. Wounds can heal. But once your spirit is broken, everything falls apart."
Old fic I decided to finish after 6 years. Help, it never left my head, lol. Moved from Fanfiction.net because I literally forgot my login info. Big quality shift about halfway through.