Crocodiles. Even when someone tries to make them look funny, as in the Disney version of Peter Pan, they still come off as menacing. Nothing looks more like a carnivorous dinosaur than a crocodile. Then there's their demeanor: they just lie around literally like logs, soaking up the sun, until they're ready to assassinate something. Sharks get all the bad press, but on three continents crocodiles kill people every year: Asia, Africa, and that no-so-safe-as-the-tourism-authority-would-like-you-to-believe land, Australia.
No wonder they live a long a time. Except for eating and reproducing, all they do is eat and swim. Sounds like some ex-neighbors of ours.