Jurassic Park nothing. The most terrifying dinosaurs are the ones that walk among us today, in real life.
In light of recent events, we feel it necessary to remind the public that dinosaurs still exist and that, yes, feathers can be scary:
Exhibit A: "The Zombie Tit"
The Great Tit seems like a gentle enough bird, that is until you learn that its nickname, "The Zombie Tit," refers to its proclivity for seeking out hibernating bats, crushing their heads AND EATING THEIR BRAINS. [Warning: Link features bird and bat demise]