Tiger
There are many stories told about the were-tiger in India. One goes something like this:
There once was a man who could turn himself into a tiger. The only way he could change back to human was if someone shouted a certain spell. The man told the spell to his loyal friend. One day, after the man's friend turned him back into a human, he died. The man was very upset. Soon after his friend's death, the man taught the spell to his wife. He turned himself into a tiger, and trotted off into the woods as usual. After a long day of hunting and eating, The man trotted back to his home to find his wife preparing dinner as usual. The wife did not recognize her husband. All she saw was a terrifying tiger. She did not know what to do. The man got so mad at his wife for not recognizing him that he killed her. After watching his wife fall to the floor, he realized that nobody was there to say the spell, and that he would have to stay a tiger forever. So the furious were-tiger walks around, killing every man he sees. He's still out there, lurking around, today.