Repulsive as Mary Lou may be.... She doesn't come anywhere close to Umbridge.
However for some reason female villains can really be more evil than their male colleagues could ever be. Let's take Bellatrix... She's funny, and we love her as a villain, but if this is all real, I'd rather face Voldemort himself than Bellatrix.... At least Voldemort will make it quick. Bellatrix likes (as Dumbledore says it) to play with her food before she eats it.
Now male villains who can beat females heads over feet when it comes to being evil, and sinister: https://www.youtube.com/watch?v=IvvxwuQMrQk at 6:40 you can see they do exist.... "This is your last chance" and the smile that comes with it. But evil and scary as it may be... He doesn't manage to be as repulsive as those two women...