Sharptooth and the Plated Sharptooth, and maybe Dil and Ichy (who actually caught them a number of times, but lost them either due to each other, or, in the last case, Spike's interference.) were the only ones that seemed truly dangerous.
I think Red Claw is the best of all the rest.
We've had Sharpteeth that get beaten by dancing Yellow Bellies or chased off by eclipses or tickled by Tinysauruses.
Chomper's parents, I guess, are also formiddable, though a bit pathethic, as they bit each other in the face when trying to get Ducky.
Maybe the Spinosaurus was a bit dangerous, as he almost got Guido and even had him in his mouth once.
Actually, I think the Plated guy had the most frightening aspect, as the first villain was being used a bashing toy by Cera for a bit.
At least the Plated guy got brought down by two other Sharpteeth, one of whom he actually wounded and probably could have killed had her mate not been there. He really has nothing to be ashamed of at all, considering how Sharpteeth go.
I mean, think of it, even Sharptooth himself was brought down by five young Flatteeth whereas the Plated Sharptooth was slain by two FULL GROWN Sharpteeth (actually one, Chomper's dad, but he fought two of them.)
His demise actually seems believable in fact as something that could actually happen in the dino world, where two full grown meat eaters would take down maybe even a bigger meat eater in order to protect their son.
In fact, I'll go out on a limb, I often do, I think the fight between Chomper's parents and the Plated guy is as good as the fight between Mama Longneck and Sharptooth.
Both involve parents fighting for their son and fighting Sharpteeth for their son and maybe someone different than them too (in Mama Longneck's case it was Cera, in Chomper's parents's case, it was the Gang of Five.).
I think that actually was a big way to show the theme of the film V, that Sharpteeth and Flatteeth aren't so different.