I really want a science fiction story where aliens come to invade earth and effortlessly wipe out humanity, only to be fought off by the wildlife.
They were expecting military resistance. They weren’t counting on bears.
Imagine coming to a hostile alien world and being attacked by a horde of creatures that can weigh up to 3 tons, run at 30 km/h (19 mph), and bite with a force of 8,100 newtons (1,800 lbf).
By the time you realise that they can traverse water, it’s too late. The surviving members of your unit manage to make it back by shedding their excess gear and running for their lives; the slower ones were crushed to death within minutes.
You later describe the creature to one of the humans you captured, wanting to know the name of the monstrosity that will haunt your nightmares for cycles to come.
The human smiles as it speaks a single word, slowly and distinctly, in its barbaric tongue.