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.