Anya
Wanda's abilities, in my world, unbalanced her mind, and led to her slowly going insane. After years of stress and a lifetime of trauma and pain, she snapped, killing her mentor and her husband, and causing the deaths of half a dozen of those closest to her. She warped reality, trying to create a perfect world, but it failed, and when it did... she...
She... decimated the mutant race, reducing a three million population to under 200, with three words and the power of her mutation.
She was the most hated mutant by any other mutant on our Earth...