When you think of a dog, what’s the first thing to come to mind? Something cute and fuzzy with a mindless grin on its face? Well, true, some dogs are like that. But others are far less cuddly. So, from brutal beasts taller than men to mighty hounds that have gone toe to toe with actual bears, grab a lead – or chain – because we’re about to go walkies with the most powerful breeds of dog in the world.