It’s more like how the Borg are described as an unstoppable unrelenting all powerful force… and are stopped, relent, and are devoid of power. On paper they are one thing, on screen they are another.
With the Romulans, they tend to outsource the violence. Pit party A against B, then clean up after. Practically scavengers. Klingons, Jem’Hadar, and Hirogen I’d more readily describe as violent.