In Dragonheart, Bowen is a disgraced knight turned dragonslayer who succeeds in almost driving dragons to extinction in search of the one who he believes was responsible for his pupil's Face–Heel Turn into a Complete Monster. The last one, who eventually picks up the name of Draco, fights Bowen to a draw and suggests a way they both can survive: Draco mock-terrorizes villages and Bowen shows up to offer to "slay" him for an exorbitant fee. It works until Draco tries to take a dive into a lake that's too shallow to submerge him.
Pulled this, since it fits better in (and is already listed under) Monster Protection Racket: