So I just learned about how after the defeat at Carrhae Crassus was humiliated in a brutal way together with multiple Roman captives, by parading the mutelated head of his son and Roman soldiers around Mesopotamia, and the act of killing the man in and of itself. I also recall Valerian, after his capture, being used as a footstool for the Sassanid Emperor for the rest of his life. Were Persians/Parthians/Sassanids keen on humiliating their enemies in such an extreme manner? Was it considered to be particularly insulting or horrific at the time and was it any different from what rival states did?
The Romans were great fans of crucifixion, which is truly a horrible, agonising way to die. Allegedly the Crassus who got gold down the throat put up 6,000 crosses along the Appian Way after Spartacus' revolt (Appian. 13.120) to punish the rebellious slaves he captured in the third servile war. Not to mention beast hunts and gladiatorial combat where condemned men were expected to fight insurmountable odds so their execution provided entertainment to the masses. Nero kept a castrated slave called Sporus as a wife according to Suetonius (Nero 28, 46, 48-49), and Tiberius directly or indirectly authorised the rape of a young girl so that she could be executed alongside her older brother for being the wrong man's (Sejanus') daughter. It was decided she had to be violated because Roman law forbade the execution of virgins (Tacitus. Annales. 5.9).
Away from domestic debauchery, the Roman triumph was an exhibition in humiliation. Vercingetorix, the great leader of the Arverni who defied Caesar, was incarcerated for 5 years before being paraded through the city of his conqueror in a chariot, then strangled to death. Cassius Dio suggests that Octavian wanted Cleopatra alive so he could lead her in his triumph (51.11) but in any case slaughtered the rumoured son of Julius Caesar by Cleopatra Caesarion, a rival to Octavian's own inheritance (51.15).
What I'm trying to demonstrate is that no ancient culture was any better or any worse than any other. Autocrats used (and still use) fear to extend and solidify control. Whether we believe the cruel deeds written in the sources to the letter is in one sense academic; the readers of Tacitus certainly thought the Emperors capable of such brutality, as did the Romans of their enemies to the east.
Appian – Roman History
Cassius Dio – The Roman History
Suetonius – The 12 Caesars
Tacitus – Annals
Follow up question: Some things I've read and Mike Duncan's podcast particularly brings up the idea that the Romans invented some or all of these horrible stories of abuse. Is there a consensus one way or the other about which is true or likely true?