Honestly, it depends on the monster.
The short answer to the question is that a general hunting bow can kill a human, though arrows don’t work the same way as a gun. (Guns don’t work the way Hollywood portrays them, either.) Death is unlikely to be immediate. You’re setting up a slow and painful death. They can survive for hours, and are just as likely to fall prey to infection. Even with modern hunting, you have to track the animal as it wanders off. They don’t just fall over dead.
Archery and hunting are a lot more complicated than just picking a bow. You need to choose the right tool for the job. For example, the war bow fired heavier arrows with larger heads designed to penetrate armor. Including heavy plate.
However, the real answer that usually gets overlooked with monster hunters is that you’ve got to stop thinking about them in terms of signature weapons and more in terms of investigation. The line between hunter and investigator is really very slim. This is why you see so many pulpy monster hunters doubling as paranormal investigators.
Whether you’re hunting animals, humans, or monsters, your character still needs to be able to tell what they’re looking at and bring the appropriate gear for the appropriate task. For example, you don’t go hunting a deer with the same gear that you’d bring for a bear. You don’t go after a werewolf in the same way one would a vampire, they’re different. They have different priorities, and it’s up to the hunter to be able to tell them apart from the signs at hand. Depending on the kind of setting you have, they may either need to be able to use magic or some sort of holy relics to repel the monsters.
A good example of a monster hunter in fiction is Geralt of Rivia from the Witcher. He carries two swords, one of them is steel and the other is silver. The silver sword is for dealing with certain kinds of monsters, the kind vulnerable to silver. However, the silver sword will get wrecked on normal humans and monsters that are not vulnerable to the material. That’s what the steel sword is for.
You have a character who brings a bow to every encounter, regardless of what the threat is. Then, they’re going to be up a creek if they’ve got the wrong weapon paired to the wrong monster. Depending on your setting rules, your archer could fire regular hunting arrows into a werewolf and be perfectly fine. I can tell you that they’d be a very dead archer in both the Witcher setting and in White Wolf’s Werewolf the Apocalypse where the werewolves will just soak that damage off. Bring an arrow tipped with silver nitrate or wolfsbane and it’s a slightly different story.
Sometimes, it’s easier to treat your monster hunter like an investigator. They’re solving a mystery. They need to be able to figure out what kind of monster they’re dealing with, especially because the locals may not know. This can take some fairly advanced specialized knowledge and a fairly wide array of skills if they have to go it alone.
A monster hunter is:
One part warrior. One part hunter and tracker. One part hedgemage. One part medic. One part fletcher, blacksmith, silversmith, and apothecary/chemist. One part academic, one with a fairly wide knowledge of folklore, ritual by region (multiple types, multiple cultures, especially that which has been forgotten), history, human behavior, and psychology.
Traditionally, most monsters and curses have their root in the actions of people. Someone did something wrong and putting things right requires sussing out the issue. More than that, depending on how technical you want to get with their monster hunting then those actions can create specialized, distinctly different curses or creatures that require very specific solutions. While violence may be an intermediary step and needed for surviving the experience or subduing the monster, the stabby isn’t what’s actually going to get rid of it.
For example, this Hellboy Animated short: The Iron Shoes. In this bit, Hellboy deals with a redcap. You’ll notice that he does fight him, but to kill it he has to drag him back to the Church at dawn to toss him over the threshold. Here’s the redcap entry on Wikipedia. On the list of things that may freak one out forever? In the modern world, redcaps look a great deal like garden gnomes.
There’s an advantage to going about it this way, rather than the Buffy way. It takes more work but, in the long run, it also justifies your character’s existence more. If the solution to a monster issue is as simple as “violence” or enough power applied to the problem, then there’s no need for a specialist.
If the only way to kill a vampire, for example, is with a stake through the heart then that’s actually not so bad. Once you get over the initial shock of them actually existing, it’s not so hard to get one’s hands on a wooden stake-like implement needed to take it out. However, if the stake only paralyzes it, and one must cut off it’s head and fill it’s mouth with garlic, bury the body on consecrated ground, or wait until sunrise and watch it burn, then it’s going to be a little more complicated. This is before we get to the rather long laundry list of different vampire types. (This isn’t even a complete one and whether some of these can be considered vampires is debatable, but it’s a worthwhile one. Detail is everything.)
To tie it all in, there’s a great Extra Credits about how The Witcher 3 may be one of the best detective games ever made, which helps explain some of the overlap between pulp fiction detective and monster hunter.
Below, I’ve listed a number of references. However, the key thing to really think about is the kind of monster hunter that you want, the kind of hunter that you want to write. Their place in society, what they hunt, and the skill set that they need in order to be able to do their job.
Once you’ve thought that through then figuring out what types of weapons that they use will be much easier. Remember, combat is a form of problem solving and there aren’t any universal tools. There’s the old joke about not bringing a knife to a gun fight but, in most cases, your characters are going to be trying to do the best they can with what they have available. Figure out what they need to have, build it into what they could have, and then walk it back to what they do have available to them.
Some monsters require enchanted weapons. Some monsters need a strike from a sword in order for them to be put down. In some cases, a bow might be better for distance or against one that might take flight. Spears are the common hunting implement for dealing with large and dangerous animals like boars. Traps. Snares. Pits. The possibilities go on and on. Ultimately, the more possibilities that there are then the more ways there are to solve a problem.
The question here isn’t what’s right? It’s what’s right for my character?
References and Resources:
The Last Wish by Andrzej Sapowski (The Witcher book series) – Though your most likely to find them in the “Tie In” section of the bookstore now due to the game’s popularity, these are what the Witcher game series is based on. Geralt is one of the best monster hunters I’ve read about and this collection of short stories focuses on the struggles he faces in navigating the human issues surrounding his job as much as it is about the monsters he hunts.
The Witcher: The Wild Hunt – The other two entries in the series are very good, but The Wild Hunt is excellent in terms of it’s world building and it’s focus on detective work. If you haven’t jumped on the hype train yet, then look at this one.
Hellboy – Mike Mignola’s Hellboy comics are famous and Hellboy as a character is probably more fascinating than he should be at first glance. There’s an interesting exploration of H.P. Lovecraft’s Cthulu style mythos while also drawing heavily from Folklore and myth. Hellboy isn’t human, but he’s very sharp and intelligently written. There’s a lot to be gleaned from him when trying to build a monster hunter. In terms of other entries, I recommend the animated over the live action. Hellboy: Blood and Iron is a particular favorite of mine.
Hunter the Reckoning – White Wolf’s Hunter RPG is really about normal people given supernatural powers by a traumatic exposure to monsters and then go out to try to kill them. It’s at it’s best when paired with the rest of the books so that you can compare and contrast perception with reality. Characters dealing with misinformation and a lack of information, trying to put what’s in front of them together without having the tools to really do their job. It’s helpful to look at, even though it’s modern, to decide whether or not this is the kind of underdog that you want to write.
Dark Ages Inquisitor – What it says on the tin, this was White Wolf’s Hunter for the Middle Ages. Helpful, if you like Hunter and want to play it in a medieval setting.
Hunter the Vigil – Almost impossible to find, terribly expensive, and penned primarily by Chuck Wendig, this entry into White Wolf’s revamp of their World of Darkness setting isn’t my favorite. Like the others in the series, it lacks some of the general oddness which made the Old World of Darkness so fun to delve into. However, it and it’s subsequent books an excellent grab for any writer that wants work with Urban Fantasy. Like the others in this series, it’s more of a toolbox than a setting. One that’s chock full of ideas waiting to be pondered and story seeds to be nabbed.
Law & Order – At the end of the day, stories based on the supernatural are often stories about people. All stories, really, are about people. Not only is Law & Order a fantastic procedural, it can teach you a lot about observation, detective work, and why people commit crimes (and why they sometimes get away with it). At the end of the day, whether it’s real or supernatural, monsters are created by people. Homicide is an excellent choice to pair with this, one to study procedure while the other is a character study in the effects of the job. Understanding both helps to really write well.
The Tony Hillerman novels – particularly all those starring Detectives Jim Chee and Joe Leaphorn. These are set on the Navajo reservation and star Navajo Detectives. Well known for their accuracy, they’re interesting to read about in general but especially helpful when you want examples of well-written tracking in fiction.
Lord of the Rings – Aragorn mostly. The classic example of the ranger.
Dungeons & Dragons – The Ranger class is for you. I’d look up associated class skills too. This is how you build Aragorn.
Folklore from as many cultures as you can get your hands on, even with European folklore much of it is uniquely dependent on different countries, cultures, and histories. So even if you’re staying within the traditional vein of European monsters, don’t limit yourself to just the British Isles, look at France, Spain, Portugal, Italy, Germany, Poland, Norway, Sweden, Iceland, Greenland, spin the globe, pick a country, look into it. I’d also study up on the same cultures’ histories and socio-political climates.