While hadrosaurids and other popular herbivorous dinosaurs could work as an antagonist, I don't think they should be the main antagonist. Even for modern animals, it is hard to make the herbivore the main antagonist of a film or series unless anthropomorphized.

But they could work well as a secondary antagonist or as a very present threat. Jumanji's newer films has done this with the hippo, and King Kong 2005 made Brontosaurus more of dangerous than Venatosaurus in that scene.

As for killing, I can only see trampling, maybe biting, and ramming. The motivation is mostly limited to just being territorial. Or remembering bad experiences with humans, akin to how elephants keep grudges.

I think they'd work for, say, secondary antagonists, or in a scene or two, but not as a main one. Personally I'd find the movie to be boring if that was the case. But yeah, hadrosaurs need to be shown as more than punching bags in films.

Biting, ramming, using their tails, etc. Can't think of any other way hadrosaurs could kill someone. If we add iguanodonts, thumb spikes

There isn't much you can do with them. I suppose you could have them seeking revenge on people who get too close to their young, but that's about it.

For duckhunt's prehistoric market I thought of a scene where the protagonists accidentally wander in a herd of diplodocus and are nearly killed

This is straight ftom httyd

What are you talking about?

The parasaurolohosaurus in the image

That's from before httyd

Oh