Dragonflies are hunters; big dragonflies not only hunt flies and the like, but also smaller dragonflies and damselflies.
When it is a matter of who-eats-whom, size does matter; there is little friendliness and political correctness in nature.
To show how big the blue emperor (Anax imperator) I posted about yesterday really is, I blended in a photo of the relatively well-known azure damselfly (Coenagrion puella), to the same scale:
Combination of two of my own photos
You won't find such a cute scene in nature; the damselfly would be lunch in seconds.