One of the things I like about the gritty, grimdark world of the Witcher is how the local people fear and dislike Witchers. It keeps them on the road, keeps them moving and provides a reason for them to stay adventurers instead of settling down with the fortune they acquired in that trolls horde. It’s always seemed strange to me that adventurers who saved the village wouldn’t capitalize on this with free accommodation in the local inn. Discounts at local traders. Free spell casting at the temple etc.
I spent a while thinking about how to make the world a little grittier to make this not the case. Maybe a class that locals might fear but still need. Or an organization that the party could belong to that would bring this out. But then I realized that ALL adventuring parties by their very nature could already fall into the same social niche that a Witcher does. If you look at it from the perspective of an ordinary villager—someone who just wants their crops to grow and their children to stay alive—adventurers can be just as unsettling as the monsters they fight.
I don't personally aim for a gritty world, and definitely don't like grimdark, but I do think this is something you can pursue as a realism thing in the right contexts. I'll add at the end how I've addressed this, in a less-gritty but still hopefully semi-realistic understanding.
Firstwise, before we touch anything else: Much of your unstated baseline appears to be that adventurers do not go to
cities very much. That they mostly spend their time in places where guards and knights and such are rare to nonexistent, other than the citizens themselves acting as militia in addition to their everyday lives. This induces certain perspectives on what makes things "gritty" that would not necessarily be true about cities. In cities, for example, it should be at least
somewhat understood that there are mercenaries offering their services, for example at the local caravanserai or the like, where traders can hire guards to protect them.
I'll try to keep a focus on that villages-and-hamlets approach, just wanting to note that plenty of campaigns do not avoid cities, and some even focus on them, so you have to be careful with some of these notions. One would expect a bustling city to not really care that much that adventurers "bring trouble with them".
They bring trouble with them:
Certainly a problem, but it can also be a chicken-and-egg situation. That is, the trouble is already there even if the villagers don't know it. So this
can be watchful and thoughtful villagers guarding themselves against real threats....and it can also, even simultaneously, be paranoid villagers jumping at every shadow. I mention this mostly because if your aim is higher realism, you should have
both reactions appear, sometimes separately, sometimes together. Villages are not hegemonic units, even if it is easy for it to feel like they should be.
They’re touched by the unnatural:
This, on the other hand, is a perfectly valid reason for any villager to be suspicious of adventurers. They really do consort with strange stuff. Even if
most adventurers aren't wielding demon-crafted swords or whatever, it's likely that at least one member of the party is in some way Kinda Weird™ and thus warrants careful handling. Just keep in mind that "careful handling" doesn't necessarily mean an actively or even passively
hostile response. It just means the villagers are all "I'm keepin' my eye on you..." or always pause and stare when the group (or at least the Especially Weird PC) is passing by. "We'll take yer money...but we ain't yer friends" kind of thing.
Their motives are unclear:
At first, certainly. This is a sense in which villagers lean Chaotic over Lawful--they judge newcomers based on their actions, not their reputation. Doesn't matter if someone is a hero of the realm, if you see them performing strange shadowy magic as they're walking into town, or the like. However, this is also the thing that needs to
adapt the most of what you've said thus far. The previous two are unlikely to change in short order, but this one can easily change from a single fight, a single "quest" completed, etc. Especially with specific types of character in the party (e.g. Paladins, Clerics devoted to good/friendly gods, and possibly Druids if they're the peace-love-and-hugs type rather than the "RED IN TOOTH AND CLAW" type), this is something that should start changing fairly quickly as the village
sees those motives in action...
BUT...it can also shift
back quickly too. It takes just one dubious action to bring past trust into question.
They’re too comfortable with violence:
This one is likely a person-by-person thing. Some folks won't mind, some will mind a lot. Keep in mind that, in medieval times and earlier, folks were a LOT more comfortable with casual violence than we are today. Bloodsport was commonplace and, especially in ancient times, often involved actual people.
Some people will follow that, and some won't. This is a good way for the adventurers to have a mix of both haters and fans in town, which can lead to a more interesting interaction space: perhaps the innkeeper hates adventurers because they've seen one too many adventurer-started bar fights, but the town blacksmith LOVES them because they know exactly what they want and pay handsomely for it relative to their usual stock and trade.
They don’t fit into society:
This one depends--a
lot. Is adventuring a long and storied career choice? Have adventurers been doing their thing for centuries? One would expect such a world to have found SOME degree of "where adventurers belong" in that context. Conversely, if adventuring has only started up in the past, say, two centuries as a THING people consider doing for a living, then sure, this can be an issue.
However, consider the reverse: what does not fit is
exciting. It's novel. It transgresses boundaries--and adventurers often do so
boldly. Confidence is a very attractive quality in a variety of ways, not just for romance. This can again create divides, and I'd expect those divides to be at least partially generational. The young, especially children and teens, may think the adventurers are just so amazing, while their parents or older villagers might find them distressing, problematic, frustrating, etc.--but they may also be
jealous of people who have such freedom and mobility. Creating a mixture of responses is a great way to give a village more life and distinction.
I guess I would need more explanation for this, because as presented, it feels like just a summary of the preceding elements. E.g. upsetting the local lord = "they bring trouble with them", while drawing in other factions looks like a mix of "touched by the unnatural" and "they don't fit into society".
They remind people of the world’s horrors:
Depends on the world having horrors to ignore. This may or may not be true of any given setting. Even in those where it is true, "remind" can be...ambiguous. People can be VERY good at compartmentalizing things. They might practice several rituals (whether because it's necessary, or because it brings peace of mind despite being useless) which only exist to repel or resist those very horrors, and then get upset about being "reminded" of those horrors despite their frequent ritual actions. That's a great way to add hypocrisy and thus some depth to the villagers.
Conversely....maybe the villagers have become too
comfortable with the presence of something horrible, and
need to be "woken up" to it and address the problem. That's an interesting position where the villagers are genuinely in the wrong for disliking the adventurers over the reminder of the world's horrors.
More or less, keep it varied. This applies to every one of the above, but this one in particular needs it the most.
What would this mean? In small isolated communities folks would likely encourage adventurers to move on. Maybe by providing clues to other adventuring activities - ideally a ways off. They might withhold hospitality. Inflate prices or claim they are out of stock to get them to move on. Similar could happen in larger settlements, but with added complications. Adventurers would garner attention as soon as they arrive. Local law enforcement and authority figures would take note of them and perhaps have them watched carefully. Ultimately the resources of the settlement could be marshaled to ensure their threat is neutralized.
None of this stops the adventurers forming strong bonds of influence and loyalty with key NPCs. But the every day Joes would want them at arms length. They remain outsiders.
It isn’t fair, but it is plausible. What do you think? do you prefer your adventuring parties to be local celebrities or like the above suggests the equivalent of a Witcher?
Because I prefer brighter (but not exclusively bright) worlds, I generally lean toward the latter. I also run a game mostly focused on the unofficial "capital city" of the geographic region it's in, like how Athens and Sparta were
functionally local rival capitals for Greece, foremost amongst its city-states. In that context, adventurers are a
useful tool, which has been integrated into the system. That brings legitimacy, but it also brings increased attention and expectation--it's never an unalloyed good.
For folks who
do want to do this kind of thing, I think the best answer is that there should not be a single pattern. It should vary, a lot. From region to region, from one town to another, hell it should vary even
within a single small hamlet with different families having different opinions. A "general store" owner might dislike adventurers for bleeding them dry of specific materials or goods, while (as noted) a blacksmith or alchemist might LOVE when adventurers come by because that's BIG BUCKS time. The town mayor might view every adventuring party as a tool to increase her power, while the local church might be welcoming to adventurers but only on the condition that they make a donation and do a little
charity work adventuring for which "divine favor" is the compensation. A tavern might love adventurers because they spend big, or they might hate adventurers because they destroy furniture too much. One family might love adventurers because Ma and Pa got saved by some when they were just married, while another family might hate adventurers because, when they fought off the orc raiders a decade ago, the combat was in the field and ruined that season's harvest, nearly costing the family their farm. The village children might run in fear, while the youths might abandon their duties to ogle the adventurers, the adults bristle at the imposition, and the elderly hail them warmly because they remember the night adventurers saved the whole damn town, fifty years ago.
Giving each place its own unique mix is important to making things not become stale and repetitive. If
everyone is always unfriendly-bordering-on-hostile, it doesn't make the world feel gritty, it makes the world feel full of
ungrateful jerks. If everyone is always friendly, it can make the world feel hollow and plastic. Mixing it up, having people change their minds based on demonstrable evidence, and considering the individual context for each NPC, is how you make this truly add depth and interest to a world, rather than superficial facades.