Danger: Humans
If you recall the climax of HG Wells’ WAR OF THE WORLDS, you might imagine the poor, highly organized and highly unified Martians coming to many of these same conclusions: and certainly the Kzin in Larry Niven eventually did, and an entire story arc of Marvel Comics was concerned with the Skrull coming to a similar conclusion.
Myself, I regard this as an amusing bit of Campbellian self-flattery, in which his writers, Asimov and Heinlein liked to follow. Not all writers are so optimistic: The Overlords of Delgon are more sadistic, the Eddorians more warlike, the Peacekeepers more disciplined, the Borg more cohesive, the Daleks more relentless, and the Romulans have pointier ears.