It depends on how you define dangerous.
The mosquito could be said to be the world's most dangerous animal.
It has been estimated that mosquitoes transmit diseases to almost
700 million people annually resulting in 2 to 3 million deaths
every year. Yet, on the other hand, millions more people live with
the mosquito, suffering no more ill effects than an irritating
Domestic dogs are dangerous. Each year in the US there are
thousands of bites, and in 2010 there were 20-30 fatalities.
Domestic dogs probably killed more people worldwide than sharks.
The danger results from the fact that there are so many of them.
Much hype has been made of the fact that donkeys kill more people
annually than sharks do, or than those who are killed in aeropane
accidents. By proportion, however, this is still a relatively low
Venomous snakes are dangerous. In India they kill between 46,000
and 50,000 people each year - a staggering figure. They are
dangerous because of a high human population density and lack of
emergency care after bites.
The irukandji is a tiny jellyfish found in the northern waters of
Australia. Its venom is 1000 times more potent than a tarantula's,
and 100 times more potent than a cobra's. However, deaths from the
irukandji are few and far between. Its cousin, the box jellyfish,
Humans are particularly dangerous. Humans have driven most
dangerous species to low population levels, and cause massive
extinction and habitat loss. For every human killed by an animal,
thousands of animals are killed by humans. Then there is the
genocide that occurs, when people turn on other races, such as
hitler's decimation of hundreds of thousands of Jews and Romanys in
World War II. No other species is responsible for so many
indiscriminate killings of its own kind, whether through war,
accidents (e.g. vehicles), manslaughter or murder, as well as
killings of other creatures.
The mosquito. It kills more than 2-3 million people a year. Thanks to its ability to spread disease with alarming efficiency. Best known for spreading deadly malaria, mossies also spread elephantiasis, yellow fever, dengue fever and West Nile virus, which was recently introduced to the US and is now prevalent in all states.
belive it or not its penquins, they rarley (but do) realase an extremely posinous venom in to its prays mouth and it slowley eats away at there organs and kills them! so dont get on the wrong side of a penquin!