Pteranodon
Pteranodon is a species of pterosaurs. This will always make the list of scariest dinosaurs because of the fact that it flies and can swoop in anytime to take a bite off its prey. This is one of the most studied pre-historic animals because of the fact that about 1,200 of it have been unearthed. A good percentage of them are preserved well in museums and labs all over. They sowed terror in what is now called North America.