For size and power:
* As big as a house - Emphasizes sheer scale.
* Like a lumbering tank - Highlights their slow but unstoppable force.
* As powerful as a bulldozer - Illustrates immense strength.
* Like a giant, scaly mountain - Emphasizes their size and dominance.
For speed and agility:
* As fast as a cheetah (for a velociraptor) - Highlights their swiftness.
* Like a lightning bolt (for a smaller, swift dinosaur) - Emphasizes their speed.
* As graceful as a gazelle (for a dinosaur with long legs) - Highlights their elegance.
For danger and ferocity:
* As dangerous as a lion - Emphasizes their predatory nature.
* Like a razor-sharp blade (for a dinosaur with sharp teeth) - Highlights their lethality.
* As fierce as a tiger - Illustrates their aggressive instincts.
* Like a walking apocalypse - Emphasizes their destructive potential.
For uniqueness and strangeness:
* Like a living, breathing myth - Highlights their long-extinct nature and awe-inspiring size.
* As bizarre as a creature from a dream - Emphasizes their unusual features.
The best simile will depend on the specific context and the effect you want to create.