Charm and looks aren't actually related.
Strictly speaking, Charm isn't about a person's looks, but is linked towards their instinct and affinity to convey affection. Charming people could easily create positive feelings with other humans and tame beasts, as well as acquire assistance from strangers.
An ordinary person's Charm levels are above ten—it's already outstanding to be above twenty. Exceeding fifty meant extraordinary applications and could be described as a natural skill—the level of beauties who carved their name into history. To improve upon that mere charm and beauty would not be enough… That requires succubus or fairy bloodlines that contain unnatural magical elements.
As for Charm of negative values, it's not to say that those people are disgusting—it's more that they have a stature that was far too dominating.
