The number 1 scariest looking dog is the Great Dane.
Great Danes look pretty scary and can be scary and cause severe injury or death to someone but some Great Danes are actually pretty gentle dogs when they trust you.
Other dogs that are on the list of the scariest looking dogs are.
Cane Corso.
Dogue de Bordeaux.
Dogo Argentino.
Boerboel Mastiff.
English Mastiff.
Perro de Presa Canario.
Caucasian Shepherd Dog.
However although some of those dogs may look mean or scary doesn't mean they actually are.
But still be careful around any dog you don't personally know.