If I may, I'd like to add that having the primary role as a villain often leads to not having much face time as a character.
While they may have a multitude of facets to their character (ie personality), there is a good deal of blowing up that comes with the territory.
Medusa reminds me of Skorne, the main enemy of Gauntlet Legends. This a character that is quintessentially representative of evil and all that this entails. However, throughout the progression of the game, he is a character that is hardly represented; though in the meantime he is still the major driving agent for all that antagonizes the 'heroes' overall.
An example
So while Bowser is sitting at home in his castle, he is still the proprietary driver of "villainry" even when we don't get to see him that much.