Saint Bernards were bred as search and rescue dogs, so they are independent. Training older, set-in-their-ways dogs to be obedient is much harder.
Although shih tzus are good-natured and vigilant watchdogs, their independent spirits make them less compliant than other breeds.
They do not require a great deal of attention, but they are stubborn and may resist training. Since they were designed to operate independently.
They are large, enthusiastic, independent dogs with a sense of adventure, but their stubbornness makes them so difficult to train.
Their innate stubbornness and amusing antics get them into trouble, as they prefer to play rather than comply with instructions.
Pugs, despite their intelligence, are extremely stubborn & difficult to housetrain. Their outgoing personality & general silliness, however, compensate for their mischievousness.
Akitas are notoriously difficult to train. Unfortunately, their stubborn nature means they aren't the best choice for first-time dog owners.
They are the sort of dogs that will test the limits of their trainers' patience during training to see how far they can get away with disobeying.
Great Pyrenees can be difficult to train because they are headstrong and refuse to take direction if given the chance. You must earn their esteem before you can expect it.