What is the most lethal toxin?
Botulinum toxin
Botulinum is the most acutely lethal toxin known, with an estimated human median lethal dose (LD50) of 1.3–2.1 ng/kg intravenously or intramuscularly and 10–13ng/kg when inhaled.[2]
Pumiliotoxin
Pumiliotoxins (PTXs), are one of several toxins found in the skin of poison dart frogs. Closely related, though more toxic, are allopumiliotoxins, (aPTXs). Other toxins found in the skin of poison frogs include decahydroquinolines (DHQs), izidines, coccinellines, and spiropyrrolizidines. Pumiliotoxins are very poisonous in high concentrations. Pumiliotoxins are much weaker than batrachotoxins, ranging between 100 and 1000 times less poisonous. There are three different types of this toxin: A, B and C, of which toxins A and B are more toxic than C. Pumiliotoxins interfere with muscle contraction by affecting calcium channels, causing partial paralysis, difficulty moving, hyperactivity, or death.