When considering the question of which shark species are the most dangerous sharks in the world, there are several factors that must be taken into consideration. There are nearly 400 species of shark and only 39 of them have ever proven any danger to humans. And even of those 39 species, only a handful can truly be termed dangerous to humans. To determine the danger of a species based solely on how many people they bite would also be misguided. Factors such as where the shark lives have to be considered, as a species can be considered more dangerous if humans run a higher risk of actually running into one. The percentage of attacks to fatalities is also important. Certain sharks style of attack lend itself to a lot of bites but most are relatively minor. Unfortunately for humans, even a minor bite can have serious consequences. Based on all of these factors combined a more accurate picture of the most dangerous shark species emerges.
Based on all data involved the Bull Shark (Carcharinus Leucas) is the most dangerous shark to humans. The species can reach sizes of 11.5 feet in length and a weight of about 700 lbs. Part of the reason they are so dangerous is the waters they inhabit. Bull sharks generally prefer shallow, murky waters that are off sandbars and reefs where people are likely to be. They are also the only shark known to be able to survive and live in fresh water. The bull shark has been found in the Mississippi River, the Amazon River, and the Ganges River, just to name a few. This makes it even more likely that bull sharks and humans will encounter each other. While they may not have the highest number of attacks, 110 as of 2008, but out of those attacks there have been 23 fatalities. This gives the bull shark a 21% fatality rate, much higher than any other shark species. Even though the bull shark normally is in shallow water where help should be readily available, their attack style makes them much more deadly than other sharks. These sharks truly live up to their namesake, the bull. They are tough, determined, and once they decide they are going to bite you they are not likely to give up easily. Bull sharks have been known to bite a victim multiple times to weaken them and try to take them to deeper water. They are truly a shark that should be avoided.
The Tiger shark (Galeocerdo cuvier) is also a species that can be very dangerous to people. They can grow to sizes of 14 feet and weigh up to 2000 lbs. Typically they are not particularly aggressive and can be rather shy at times. They typically troll for prey slightly offshore, so most of the encounters with humans will be surfers, kayakers, or divers. Since the tiger shark is used to their prey being very tough (mainly sea turtles), an initial attack by a tiger shark may be more aggressive than with other species. Tiger sharks are also notorious for consuming things that may not have much nutritional value. They are not only active predators, but scavengers as well, so they often bite things that are not their usual prey. There have been a documented 145 attacks on people, up until 2008, slightly more than the bull shark. But only 28 of those attacks have been fatal, giving the tiger shark a 19% fatality. This can probably be attributed to the fact that a lot of attacks take place farther from shore where help may not be readily available.
Finally at the third most dangerous we reach the Great White shark (Carcharodon carcharias). The white shark is the largest predatory fish in the sea, at lengths of over 20 feet and weights exceeding 4,200 lbs. The typical prey of the white are large marine mammals like seals and sea lions, although they have been known to scavenge whale carcasses as well. Their usual hunting range is off shore, in the surf, where seals are likely to be navigating to and from the shore. While the great white has the most documented attacks of any other species at 430 as of 2008, but on 63 of those have proven fatal. That gives the white shark a 14% fatality rate. Most of this is due to the attack and hunting style of the white shark. Seals and sea lions are very large prey and can cause the shark a lot of injury. So the white shark will usually bite hard enough to sufficiently wound their prey then back away while the prey becomes weak with blood loss. Then the shark can move in and safely consume its meal. This bodes well for any human who is mistakenly thought to be dinner. Since the shark will make a medium force bite and then back away, giving the injured human time to get back to shore.
The Oceanic Whitetip shark (Carcharinus longimanus) is often overlooked on lists of dangerous sharks. But some scientists theorize that this species is likely responsible for more deaths and attacks on humans than all the other species put together. It is a slow moving fish that usually only reaches lengths of about 13 feet. They stay far out to sea and only put on short bursts of speed to catch prey, they are very unlikely to encounter a human. Until that human is stranded in open water after a plane crash or a boat wreck. This leaves humans stranded in the water with rescue being many hours away. Unfortunately it usually only takes an hour or two for the oceanic whitetip to find them. Once on the scene the whitetip is quick to become aggressive and the stranded humans have no defense against them. However, hundreds or possibly thousands of human attacks have not been attributed to the oceanic whitetip since a lot of the bodies of these disasters are not recovered and surviving victims usually cannot identify the sharks involved. Even the famous oceanographer Jacques Cousteau described the oceanic whitetip as "the most dangerous of all sharks"
Several others species are considered dangerous to people, to varying degrees. However, the chances of encountering them are highly unlikely unless you are a diver, and their fatality rates are very low. So while they may be dangerous and should always be approached with caution, they are less of a threat to the general public as the others listed.