Dinosaur Rivalries: Tyrannosaurs vs Ceratopsians

Psittacosaurus vs Raptorex

Protoceratops vs Alectrosaurus

Diabloceratops/Machairoceratops vs Lythronax

Chasmosaurus/Centrosaurus vs Daspletosaurus (all three lived together)

Pachyrhinosaurus vs Gorgosaurus/Albertosaurus (again, all three lived together)

(God...I can't believe I'm using a scene from this abominable movie)

And of course...

Eotriceratops/Triceratops vs Tyrannosaurus rex