I can tell you one animal I certainly wouldn't get into a fight with, the.....
HONEY BADGER! From wiki:
" Its ferocious reputation extends to attacks on animals much larger than itself. Several African tribes report that the honey badger attacks the scrotum of larger mammals if provoked and has even castrated humans. While these reports remain uncorroborated by firsthand evidence, there is some circumstantial evidence such as remains of castrated waterbuck and gnu found in Kruger National Park.
The honey badger can eat dangerous venomous snakes, most often the puff adder. If bitten the honey badger will become severely swollen and paralysed unable to move for two to three hours. After this period of time the honey badger will re-awaken and continue with its meal or continue its journey. Even more tenacious, is that a honey badger will gladly steal a snake's kill, eat it for itself then continue to hunt the snake. This ferocious nature of the badger has earned it its image as a formidable creature "