Beautifull, but harmless.....?

Indian Cobra

The Indian cobra's venom contains a powerful post-synaptic neurotoxin. The venom acts on the synaptic gaps of the nerves, thereby paralyzing muscles, and possibly leading to respiratory failure or cardiac arrest. The venom components include enzymes such as hyaluronidase that cause lysis and increase the spread of the venom.^[8] Symptoms of cobra envenomation can begin from 15 minutes to two hours after the bite, and can be fatal in less than an hour.^[9] The Indian Cobra is one of the Big four (most dangerous venomous snakes of India) and a polyvalent serum is available for treating snakebites by these snakes. Despite its fearsome reputation, only 10% of the bites in humans result in death.
Poison Dart Frogs

Poison dart frogs, wear some of the most brilliant and beautiful colors on Earth. Their coloring can be yellow, gold, copper, red, green, blue, or black. Their elaborate designs and hues are deliberately ostentatious to ward off potential predators, a tactic called aposematic coloration.Dendrobatids include some of the most toxic animals on Earth. The two-inch-long (five-centimeter-long) golden poison dart frog has enough venom to kill 10 grown men. Indigenous Emberá people of Colombia have used its powerful venom for centuries to tip their blowgun darts when hunting, hence the genus' common name.

batrachotoxins, prevents nerves from transmitting impulses, leaving the muscles in an inactive state of contraction. This can lead to heart failure or fibrillation. Alkaloid batrachotoxins can be stored by frogs for years after the frog is deprived of a food-based source, and such toxins do not readily deteriorate, even when transferred to another surface. Chickens and dogs have died from contact with a paper towel on which a frog had walked.
The average dose carried will vary between locations, and consequent local diet, but the average wild P. terribilis is generally estimated to contain about one milligram of poison, enough to kill about 10,000 mice. This estimate will vary in turn, but most agree that this dose is enough to kill between 10 and 20 humans.

Stone Fish

Its dorsal area is lined with spines that release a venomous toxin. It is the most dangerous of known venomous fish and its venom causes severe pain with possible shock, paralysis, and tissue death depending on the depth of the penetration. This level can be fatal to humans if not given medical attention within a couple of hours.
The pain is said to be so bad that the victims of its sting want the affected limb to be amputated

Inland Taipan

A single bite from the Inland Taipan contains enough venom to kill as many as 100 human adults, or 250,000 mice. The average venom yield of this snake is 44 mg, with a 110-mg being the largest recorded yield. Its venom is 50 times more toxic than that of the Indian Cobra and 650 - 850 times more toxic than that of a Western- or Eastern Diamondback. The Inland Taipan has an extremely neurotoxic venom which can cause death to an adult human in as little as 45 minutes

Box Jellyfish

Their sting is incredibly powerful and extensive stings can be rapidly fatal. The sting produces excruciating pain accompanied by an intense burning sensation, and the venom has multiple effects attacking the nervous system, heart and skin at the same time. While an appreciable amount of venom (about ten feet or three metres of tentacle) needs to be delivered in order to have a fatal effect on an adult human, the potently neurotoxic venom is extremely quick to act. Fatalities have been observed as little as four minutes after envenomation, notably quicker than any snake, insect or spider and prompting its description as the world's deadliest venomous animal. Although an antivenin exists, treating a patient in time can be difficult or impossible.

Broken tentacles remain active until broken down by time and even dried tentacles can be reactivated if wet.