Since I apparently never compiled it, here are my findings and theories on vampire weaknesses.
First off, the concept of almost all human-eating monsters like vampires, ghouls, wendigos, etc seems to have come from the idea that people that had no food would resort to cannibalism. Which has been used as a joke in skits about landing on a deserted island for who knows how long. Generally, in European folklore (at least I think it's European? Might be more specifically Christian Europeans, since most sources I've read make mention of crosses, crucifixes, etc), the aristocratic or otherwise more charming people became vampires, while people in poorer conditions would be called ghouls. Alternatively, a ghoul was either a completely separate entity, or a subspecies of vampires. Considering the concept of vampire thralls in fiction, my theory is ghouls are thralls with no master but no blood, like, they were abandoned or killed their master. Might be an evolutionary split, where some flesh eaters become ghouls straight away (a ghoul's bite is said to turn you into a ghoul; maybe ghouls are those drained by a vampire but not fed the vampire's blood?) while some are thralls that never got more than two drops of their master's blood.
Most weaknesses have a logical and mythical explanation.
-Garlic: Garlic is strong. If someone has become used to flesh or blood, especially fresh or raw, the taste of garlic probably overloads them. Usually a large amount is used, too, think like pocket sand. It's also possible they just don't like garlic. Spiritually, people saw the health benefits of garlic (or heard claims about it) and figured it was some sort of sacred food.
-Sunlight: The sun is a deadly laser. Bodies seem to break down faster in direct sunlight. Spiritually, well, the sun is said to be holy. Some say it's where the divine live, it's a gateway to the good afterlife, etc. Others say it's the first creation of God, though technically He made light, whether he made the sun specifically is unknown.
-Stab through the heart/Cut off the head: Probably tried and true. Considering they were living people...yea...that being said, I'd assume reanimated bodies that aren't explicitly controlled by outside sources like fungi and magic probably need their organs to function. This one has no spiritual explanation, it just makes sense.
-Can't enter unless invited: May have been made to trick people that think they are vampires, this is more about being able to enter when the owner is aware you are entering, as if you're caught sneaking in, well, you're up to no good. Spiritually it was believed that a house was protected by the divine; witches, having lost divine favor, had to replace that protection with magic. This makes no real sense as a hard and fast rule, but seems to be a social norm.
-Running Water: It's never really made clear what running water is, specifically. Usually a stream or river or natural water, even when stagnant, there's no real logic, though it may be a trick to stop vampires from chasing someone. Spiritually, many afterlifes have some sort of body of water, so it may be that if the undead walks over physical water, the deity in charge might notice they are undead and drag them back in. Another possibility is that all natural water is charged with God's gift of life, so it hurts like holy water.
-Holy Water/Oil: It's salt water or various chemicals in oil that is probably getting in their eyes, nose, maybe even a wound. Spiritually, vampires have no soul, so anything holy hurts them.
-Silver: Not even specifically silver, but, it's metal blades, shit hurts. People saw how silver reacts to poison, so, spiritually, silver is said to be one of two sacred metals (guess the other one). This is also why old mirrors supposedly didn't reflect them, but we nowadays know that's not how mirrors work. Some say they don't cast a shadow for a similar, soulless reason.
-Wooden Stake: It's sharp wood piercing weakened flesh. Spiritually, it was usually some sort of sacred wood specifically.
-Alcohol: A rarer one, some sources say alcohol has a stronger effect on the undead. May be based on them being a disinfectant. Or because their organs are in worse health. Or because they like drinking. Spiritually, I have had a hell of a time trying to find spiritual uses for alcohol outside of wine being Jesus' blood and as deity offerings. Not just for this, but in general!
-Crosses, Bibles: This is actually a funny one, these don't even hurt the vampire, historically! So basically, the idea is that, if a vampire sees any Christian symbol, they will recall the afterlife they had lost, and weep, crying over no longer feeling God's love! So obviously this doesn't work on atheist vampires, and changes based on their religion. A lot of fiction instead has the divine symbols burn them; I'd think by that logic, any divine symbol that embodies a good deity would work.
-Salt/Fine Grains/Knots: In some traditions, vampires have OCD and will be compelled to count anything out of place. Another physical logic is, it's salt or other fine grains, you probably threw it in their eyes. Spiritually, salt is said to purify all it touches, based on how it cures meat. It's also said to be the remains of the original Earth before the great flood. Theoretically,by that logic, sea salt is the best option, though pink salt may make them tempted to eat some.
-Specific Blood: This is mostly fictional sources, but, these bloods have different effects on vampires:
-Animal Blood: Yada yada vegan vampires look nobody that likes actual historical vampires takes Twilight seriously (not saying they don't enjoy it, but), so, I'm going to put this out there: some stories say vampires can drink animal blood but get more nutrients from humans, others say animal blood doesn't taste as good, the reality is if animals were an option vampires wouldn't have existed. One thing I sort of agree with Twilight on is vampires that stick to animal blood are probably spiritually purer than human drinkers.
-Dead Man's Blood: Realistically, unless the person just died, any blood left in there is probably dried up. Hell, blood in a corpse is sometimes a method to GET vampires! Not sure if it hurts them like in Supernatural, but why would it?
-Spirit Blood: This is sort of banking off of the last one, but, in stories where ghosts can have physical bodies (think like youkai), the blood of theirs can burn them. This sort of is cheating, since in the main series I've seen it, Touhou, there's a method to become a "celestial" without dying by eating immortality fruit, usually peaches from the Buddhist Heaven, so this may be like holy water.
So, how can you make the ultimate anti-vampire mixture, for your vampire hunting kit? Soak plenty of garlic in alcohol or water, which has been blessed, and which has been charged with sunlight. After about a month, filter it out. Offer it to them as if it was a normal drink, or sneak it into their glass, or use it as an ointment to ward them off.
