Speaking of Kid Icarus, it's got me wondering about villains in Smash (using it in the broadest possible sense so don't give me the full "actually an anti-hero" speech)
Mario has Bowser, nepotism and a minion
DK has the King
Zelda has the guy I kept accidentally calling Gandalf when I was a kid and driving my friends bananas
Metroid has Ridley and Dark Samus
Kirby has Meta Knight and THE King
Star Fox has Star Wolf
Pokemon has Mewtwo (Basically Final Boss of Gen 1) and Greninja (Dark Type, told you it was broad definition)
It seems like most of the bigger ones are covered except Yoshi who is doomed to be set up against baby Bowser for all eternity even when he got rid of Baby Mario and Fire Emblem who only has only Sword wielding lords and Robin (Tactician instead of lord)
Which brings me to my point, Kid Icarus's closest thing to a villain is Dark Pit who because Angel Boy is too pure, is really more slightly-grouchy-with-independent-streak Pit. Uprising had so many factions it's hard to say who would be a more definite villain in Smash.
Medusa is Palutena's dark counterpart but is a red herring in Uprising.
Viridi is antagonist for most of the second act but is part of the Guaidance system in Smash
And then there's Hades who seems more suited for a Boss role with his powers.