The top ten most vicious dog breeds are Great Danes, Boxers, wolf hybrids, Malamutes, Huskies, Bull Mastiffs, Doberman Pinschers, German Shepherds, Rottweilers, and Pit Bulls. These breeds can be great companions if cared for properly, but their size and strength means that they can be dangerous if they are mistreated.
Great Danes are dangerous because of their sheer size - they weigh up to 200 pounds and stand 86 centimeters tall. The last recorded killing by a Great Dane was in 2003 in South Carolina. Boxers have long been used as guard dogs and are known for their strong bite. They are very protective of their family and thus can be aggressive to visitors. Wolf hybrids are crossbreeds of domestic dogs and wild animals. These dogs are unpredictable and skittish, and have been outlawed in many states. Malamutes are used as sled dogs but have strong hunting drives, which means they often attack smaller animals. Huskies were also bred as sled dogs, and do not have the social skills required of typical companion breeds.
Bull Mastiffs are physically imposing dogs, and can weigh up to 130 pounds. They were bred for guarding and thus have an aggressive temperament. The size and physical strength of Doberman Pinschers makes them a dangerous animal if not properly trained. Often these dogs are aggressive towards strangers but sometimes also attack their owners. German Shepherds have a powerful bite and aggressive tendencies towards smaller dogs. Rottweilers have an even stronger bite and were responsible for half of all dog bite fatalities in the years 1993 to 1996. Pit Bulls are the most dangerous dog breed. A 1991 study found 94% of attacks on children by Pit Bulls were unprovoked.