Slowest Dog Breeds – Over 40 Pounds Basset Hound. When you look at the Basset Hound, you definitely do not see speed. Clumber Spaniel. At only 20 inches high, this canine is still 55 – 85 pounds. Newfoundland. Chinese Shar-Pei. Saint Bernard. Old English Mastiff. Bullmastiff. 20 Strongest Dog Breeds In the World.