The monitor lizards (Varanus) show relatively little morphological variation.
The most commonly found Indian monitor lizard Varanus bengalensis is about 50 cm long. It is characterized by a large trunk, long neck and tail, large pleurodont teeth and long protrusible and deeply bifid tongue. They are active predators, feeding on a variety of invertebrate and vertebrate animals. Its dark brown body bears black spots dorsally. It is a good climber on trees as well as a good swimmer in water. (image source)
The largest living lizard in the world is the ferocious dragon, Varanus komodoensis, found on some of the Islands of Malaya Archipelago. It may reach a length of 2.5 metres and weight over 100 kg. It is capable of killing adult water buffalo with its venomous bite, but it normally preys upon wild pigs, goats, deer, etc. The keys to its killing ability is down to infectious bacteria in its saliva, which can kill prey.