Oh sorry I forgot this stream existed.
The most toxic mushroom ever is The Death Cap (Amanita phalloides) if you eat it for whatever reason you are guaranteed to die within 72 hours. The symptoms of the amatoxins are liver/kidney failure, diarrhea, vomiting, low blood pressure, nausea, and ultimately death. A similar one would be the Destroying Angel (Amanita bisporigera) which is essentially the same thing.