This is a highly subjective question as it's not clear how you'd define 'dangerous'. Animals can be dangerous based on aggression, propensity to kill at will, venom etc. There are different reasons why animals might attack, perhaps they feel threatened or a harsh winter or dry season has pushed them to hunt people. Who is the animal dangerous to? Humans? Other Animals? A lion may be dangerous to a human but an elephant may not have as much to worry about. Even then, lions are mainly dangerous when hungry or when threatened. Contrary to popular belief, carnivores are not generally more dangerous to humans than herbivores. Large herbivores tend to be a lot more aggressive than any carnivore. It's worth noting that all wild animals of a good size can show considerable aggression towards humans if threatened.
Ten Mammals Known for being dangerous towards humans;
These are animals that are usually known for being aggressive and have been known to attack humans.
10. Mustelids (Wolverines, Badgers)
9. Deer (Moose, Elk, Red)
8. Dogs (Wolves, Coyotes, Hunting Dogs, some breeds of Domestic Dogs)
7. Hyenas (esp. Spotted/Laughing)
6. Bears (Polar, Brown (Grizzly, Kodiak, Russian), Black)
4. Big Cats (Lion, Tiger, Leopard, Jaguar, Cougar)
3. Elephants (Both African and Indian)
2. Bovines (Bison, Gaur, Domestic Cattle, Buffalo - esp. Cape)