I agree with @guy, great post.
I'd like to focus especially on war, since it's the cruellest activity. We understand very well that every war brings its dose of brutality and Romans were not an exeption at all; but I think that usually people don't face the issue in the right way, especially if they don't know history very good.
We tent to compare ancient civilisation with our present, not with other civilisations of the past. So, let's try a quick comparision.
ROMANS
1) In abstract terms, did Romans prefer to destroy at all the enemies or to conquer without too useless losses? 2) When they used violence, were they proud of it? 3) Did propaganda show brutality without constraints, focusing on the sorrow of the losers and bloody war scenes?
The answers are:
1) Romans' ideal way to rule was "to spare the subjected and to vanquish the proud" (parcere subiectis et debellare superbos, like Vergil wrote), so they didn't abandon themselves to gratuitous violence: why should they? Romans were very practical and they knew that mass killings costed time, money ant the result was only to create irreducible enemies among the survivors. For them it was more convient to turn enemies in subjected who paid taxes.
2) No, in that case they tried to hide it. Propaganda or not, Romans believed in the "bellum iustum" and animal violence was obviusly against this ideal. Bloody Ceasar's campaigns in Gaul were shocking for most of the senators and I believe to remember that there was a sort of investigation by the senate for this early war crimes.
3) Again, no. Romans loved to display their rule like a one which brought peace, wellness and order: in a word, "civilisation".
What I wrote above refers a lot to propaganda, that's true: but propaganda says a lot about poeple's mindset. For us it is obvious that rulers don't want to show violence against enemies and present them like good guys, but it's absolutely not a rule: it's plenty of ancient populations who, on the contary, loved to show their power by the cruel subjugation of the enemy. Here some examples from the Ancient Near East.
SUMERIANS
The sumerian army marchs stepping on the corpses of the enemies. https://en.wikipedia.org/wiki/Stele_of_the_Vultures#/media/File:Stele_of_Vultures_detail_01-transparent.png
AKKADIANS
King Naram-Sin reaches the god climbing over piles od corpses. https://en.wikipedia.org/wiki/Victory_Stele_of_Naram-Sin#/media/File:Victory_stele_of_Naram_Sin_9068.jpg
ASSYRIANS
King Ashurbanipal and his wife celebrates the victory in war with a banquet; in the right corner the decapitated head of the enemy king hangs from a tree. https://www.ilgiornaledellarte.com/immagini/IMG20180926161716647_900_700.jpeg
EGYPTIANS
One of Ramesses II's epithet was "the one who smashes enemy's head".
And so on.
There are so many other examples, everyone which celebrates the king and the army as distroyer of enemies and Mesopotamian art could be very bloody, like we'll never see in Roman art. Is it just propaganda? Right, but not every propaganda is the same and it shows the ideal world that rulers pretend to create. There are no scenes of Roman emperors who merrily feast victory while a head hangs over their head.
So, this is the problem: we take for granted that our (modern) mindset is normal in every time and every place. That isn't. Among the ancient populations, Romans were one of the less cruel; or, at least, they were no proud at all of using violence. And that makes an enourmous difference.