I remember some years ago that a bar in California was serving shots with black widow spiders in them. So, apparently you can eat the venom from a black widow without issue, and they’re pretty dangerous spiders.

Most of them would be denatured by stomach acidity but the risk of something like paradoxin finding a small route into your blood stream is too damn high.

When it comes to venom that is also used as a toxin in other species, though, and is a big killer of humans, the crown goes to https://en.m.wikipedia.org/wiki/Tetrodotoxin which is used as both a poison against predators for things like pufferfish and a venom for things like the blue ringed octopus.