So, a few months back, I had a Discord party with people from Spain, Italy and Denmark, about 5 players, I was the DM. I was DMing a Medieval Europe setting with a magical twist on it. We were playing D&D 5E.

Session 1: Every character was from a different nationality (Spannish player had a Bohemian wizard, Italian players had an Irish artificer and a Dannish bard, as for the Dannish players they were Brittish twin brothers, one was a paladin and the other was a warlock). Everyone started in their in game home country, then had to progressively make their way to get together in the city of Toulouse, in France, where the count pleaded to the party to help them fight against a goblinoid invasion of the city, mainly goblins and bugbears, a few hobgoblins in the mix, but, they were rare to see. The decision was unanimous, they would help, for the simple, but high, price of 100 gold pieces per party member, so, 500gp overall. The count told them that he would have to get the money, and it might take a week or two, but that they would be paid.

The raid started two days after the count had asked the party to help them, and the castle's defenses were pretty solid: a moat, filled to the top with water, if some managed to cross it, they would be surprised by the opening of the draw bridge, squashing them to death, while the remaining ones would have hot tar poured on top of them. The plan worked for the most part, and the party only had to fight two bugbears and seven goblins, the last survivors from the raid. By a combination of luck and a bit of my DM style (I'm usually a good guy, squashing some higher hit rolls here and there), they made quick work of them.

Session 2: In the aftermath of the raid of Toulouse, they were waiting for their payment, from the count, after one week of in game time has passed, they receive the 500 gold and go south, towards Spain, they were riding on a cart, so it would probably take them two to three days to cross the Pyrenees. On top of the Pyrenees, they make a stop, in what I described has being a fortress, with a small town of about 500 people inside (still, small when comparing to most of the cities of the time), you might know it as Andorra. This is where things get weird, for some reason they thought this was either a temporary bandit fort (yes, I use bandit forts, basically, it's a fortress that was captured by bandits and now they live there) or some sort of supernatural evil town, because, in their characters POV, nothing natural could survive in those extreme conditions -20ºC for long. They then proceed to exterminate the whole town, didn't even asked for perception checks to know if it was just a fortified town, nor did they ask for history rolls, to see if they knew or heard about people who lived that high in the mountains. I get pretty pissed off and have the town guard appear, from within the guard post, about 10 guards, there is combat, but the guard arrests them. The players are fuming, saying I should have told them it was a normal town, and that there was no danger... I told them it was a SMALL FUCKING TOWN WITH 500 PEOPLE LIVING IN THERE!!! Not even if it was Jesse James's gang it, they didn't roll for perception, to see if it was dangerous, or for history, to see if living there was possible. A lot of the town was killed, about 50 to 100 people are alive, and I swore never to play with those guys again, still good friends with them, but I won't ever play with them again.

TL;DR: Party kills a big portion of a town's population and got pissed when they got arrested for mass murder.