B12 is the important one. It isn't in a vegan diet at all. It takes years (usually) before you run out of it, but once you do, you have neurological damage. It's not difficult at all to get enough protein (we need much less than the paleo people believe) but B12 MUST be obtained via a supplement. https://www.vegansociety.com/resources/nutrition-and-health/nutrients/vitamin-b12/what-every-vegan-should-know-about-vitamin-b12#:~:text=B12%20is%20found%20to%20some,non%2Danimal%20sources%20of%20B12.