You are very correct on this. This tends to be a trend among a minority of states throughout pre-modern history. The Neo-Assyrians, Aztecs, Early Mongol Empire, etc... are examples of this trend.
This fact, that you have enunciated well, should be realized as this discussion continues.
It seems to be a repeated tactic in early civilisations. The Aztecs tried to strike fear and awe into the Spaniards with tales of how many people they sacrificed. They claimed to have sacrificed 80,000 in one religious festival. Grisly artwork depicted the fates of those who stood against the Aztecs and their gods. At the foot of the Twin pyramids of the Sun and Moon in Tenochtitlan was an immense carved stone effigy of the dismembered remains of the Goddess of the Moon after her brother Huitzilopocthi cast her remains down the steps of the temple of his birth.
At the temple of Tlaloc they kept jars filled with the tears of sacrificed children (really).
The Qin were a severe nation that dominated China due to their militarist mindset and severe laws. Once in a dominant position they ordered that anyone who owned books that were not mandated by the government would be executed and their books burned. Especially the histories of China before their unification. Chinese philosophers were buried alive in their tens of thousands.
Shang Yangs Law was far too stifling. Art, music, education, merchantilism and many other things were banned. Shang Yang believed that the stupid do not ask questions, they follow orders. He also believed even the dukes should be subject to his Law which eventually got him the Nine Familial Exterminations (his entire family line was murdered, down to 2nd cousins and then he was killed last). Within a few years of Qin Shi Huang Di's death the Qin dynasty was destroyed by an immense rebellion.
Ultimately nations that rule through abject terror require an undisturbed line of highly competent rulers. A weak link in the chain and they would be annihilated like the Assyrians, who were destroyed by simultaneous rebellion and invasion so completely they never rose again, due to a palace coup of a weak successor to Ashurbanipal.
The Aztecs capital of Tenochtitlan was destroyed mainly by the Conquistadors allies, due to their seething hatred of their tyrannical Aztec overlords.
Rule through fear alone is unwise and very risky, though we have the benefit of hindsight to help us make this assessment.
I think the Neo-Assyrians are far too wedded to their brutality to mellow and have no real contemporary examples to learn from. Each king requires a military campaign to cement their rule through terror and the first great defeat will bring the whole thing crashing down. It is always going to end violently for them. If you live by the Sword, you will die by the Sword.