battle

Don't you think maybe Walpurgisnacht cursed the Kyubey in the end?

after tens of thousands of years, she's the first witch to spark a chain of events that would eventually lead to the end of the incubators and the witch' cycle.

Kyubey also claimed they thought Walpurgisnacht wasn't a single individual. Which lead me to believe that one magical girl might've had to kill a friend, and then they became a joint witch, or she a witch with the grief of several girls. Something like that. At the end before they fall, they all curse something, usually the world, or their own shortcomings, but in this case, they might've cursed the kyubey instead?