When you get hit so hard you actually do respect (and fear) your foe

Explanation: In the early-mid Roman Republic, the Romans faced a couple of dire challenges.

First, they had an entire army captured by the Samnites, a neighboring Italic tribe. The father of the Samnite leader advised to either release them without humiliating them, or just to kill them all - because the Romans were too fucking stubborn and proud to just knuckle under after a humiliation. The Samnites, rather foolishly, opted to humiliate the Roman army (by having them walk under a yoke, representing submission) and release them.

Rather predictably, to anyone familiar with the Roman Republic, as soon as the troops returned home, they were told that they had no authority to surrender without permission of the Senate, were rearmed and reinforced, and sent right back out to fight the Samnites again. Eventually, Rome won. Stubborn fucks. This was a tale that continued to be proudly retold by the Romans in honor of their own stubbornness (very humble people, the Romans, the most humble).

Second, they had a famed Greek warlord, Pyrrhus of Epirus, attempt to stop their hegemony over the Greek colonies in Italy. Despite winning two battles against the Romans, Pyrrhus recognized that the Romans were insanely, pathologically stubborn after seeing them suffer tens-of-thousands of casualties and casually conscript more troops like it was a slow Tuesday, and opted to cut his losses while he could. This was also a tale proudly retold by the Romans in honor of their own stubbornness - and where the term ‘Pyrrhic Victory’ comes from, meaning a victory not worth the cost.

Third, during the Second Punic War against Carthage, the great Carthaginian general Hannibal scored victory after victory against the Romans over the course of a ~15 year campaign in the heart of Italy, reducing the Roman military to a hyper-defensive posture. The Romans did not proudly retell this story of repeated losses, though they did retell it - one expects not proudly because a fifth of the citizen population was killed by Hannibal, and those losses are hard to justify even by “We’re stubborn and they aren’t!” At some point, it does become “Fuck, we really messed this one up.”

Notably, despite his wily tricks and stratagems, Hannibal did not denigrate his competent Roman foes - even showing at the funeral of a Roman general he had ambushed to pay his respects. Not only that, but Hannibal was an innovative tactician who the Romans themselves could not deny the genius of. While Hannibal was alive, the Republic was terrified of him - down to hunting him even when he was an exile without an army, couch-surfing at the palaces of Rome’s enemies. But when Hannibal was dead, and the Republic could breathe easy, it didn’t take long for his reputation of terror to merge with his reputation of genius and bravery. While Carthaginians in general (or the idea of Carthaginians, rather) were sneered at, Hannibal was a rare Carthaginian figure whom one could be compared with or praise in Roman society without risk of being seen as a filthy Carthaginian-lover.

Hannibal may have been the boogeyman to the Romans, but they respected how incredible he had to be to get that reputation!