If this situation arose, and we were within a short distance of the town, we would stablize them, tie them up REALLY nice, and hand em over to the authorities (who might just outright execute them right then are there anyways). If we knew that we were a long ways from town, then we would just let them die of their wounds, not even bothering to heal them. Letting them succumb of their injuries which occured because THEY picked a fight is far from evil, and probably the most merciful of all options.