10: TIBETAN MASTIFF
Considering that this dog breed looks like a cross between a Rottweiler and a St. Bernard, it looks scary enough but another issue is that due to its size, these types of dogs get a lot of attention. As the name suggests, it originated from Tibet and was used for both shepherding as well as to guard livestock. Because they are known to be highly combative and aggressive, they need to be trained on how to play nice with others as well as get a lot of outdoor activity to release all that pent up energy.
