Gertie Simmons
Gertie Simmons is a dead Witch (by the time of Witches Abroad) who is known among other Witches as having an extremely bad squint. She was always "putting the evil influence on the end of her own nose", according to Nanny Ogg. And this posed a problem because the idea of making your own nose drop off when you get angry doesn't exactly help to inspire fear in others.
Her squint was compared to Millie Hopgood's.