What was the most dangerous dinosaur that lived during the Jurassic period?

Answer 1

The master predator was Allosaurus fragilis, "the wolf of the Jurassic." They probably hunted in packs to bring down the huge sauropods. Tyrannosaurs hadn't come on the scene yet.

Of course, "dangerous" could be "dangerous to whom?" Animals smaller than the sauropods (who could probably stand off some Allosaurus attacks) were threatened by many smaller predators that would never think of taking on the giants.

Also, creatures such as stegosaurs could be pretty dangerous to anything getting within reach of that spiked tail.