The Warlock of Qarth may have rather unceremoniously been roasted alive by Daenerys Dragons, but being overcome by the flying lizards even if they were still hatchlings is nothing to be ashamed of. In HBOs show, Pree is a master of illusion and psychological warfare, using his mystical powers to confuse, frighten and crush his wretched opponents. In The Watchers on The Wall, Giants are shown to be idiotic and driven by their dominant emotions of hate and rage. This lack of intellectual heft does not bode well for a Giant when hypothetically trying to fend off Pyatt Pree. Against the limited mind of one of these lumbering creatures, the Warlock of Qarths illusions would be even more effective. He would be able to conjure up mirror images of himself (a power he doesnt have in the books) to disorientate the 14-foot monster before using his arsenal of spells to crush the fragile mind of the Giant from within or possibly slipping a dagger in its back. It may not be a Dragon, but Pyatt Pree would surely like to exact his revenge on at least one of Westeros fantastical beasts. In a physical fight a Giant could kill a hundred of the disturbingly puny Warlocks, but armed with his magical abilities a battle with Pree would be a bad style match-up for a Giant.