Fierce Snake or Inland Taipan
The inland taipan, also commonly known as the western taipan, the small-scaled snake, or the fierce snake, is an extremely venomous snake of the taipan genus, and is endemic to semi-arid regions of central east Australia.
While I did say that I would not include multiple sub-species in this list, the incredible Inland Taipan deserves a spot of its own. It has the most toxic venom of any land snake in the world. The maximum yield recorded for one bite is 110mg, enough to kill about 100 humans, or 250,000 mice! With an LD/50 of 0.03mg/kg, it is 10 times as venomous as the Mojave Rattlesnake, and 50 times more than the common Cobra. Fortunately, the Inland Taipan is not particularly aggressive and is rarely encountered by humans in the wild. No fatalities have ever been recorded, though it could potentially kill an adult human within 45 minutes.