NintenEdgyMan
Smash Apprentice
I am going to split this into 2 sections: The spoiler free and spoiler section. The spoiler free might contain very minor spoilers, but they won't be big. It's hard to make a spoiler free thread of this matter due to the nature of villains in video games.
Spoiler Free:
Medusa ()- Medusa is the main villain of Kid Icarus and the villain in Kid Icarus Uprising (can't speak for the gameboy game because like most people i haven't played it). She is an iconic character, a character who would give Kid Icarus an easy rep, and is well liked by the community. Sure she could be unique, but loking at her backstory and even the way she fights shows that she would be perfect over Palutena.
Dark Meta Knight ()- Dark Meta Knight is the main villain in Amazing Mirror and playable in Star Allies. Although maybe not the most iconic option, they would only need a quick model swap and would give the Kirby series an easy villain, something that is difficult due to how most get redeemed. But despite how they are a dream friend, they are still portrayed as a villain.
Dark Link ()- Dark Link is simple. Just a dark Link. What they could do is they could give him the properties of Toon Link's bow and bomb to make him feel more like the old Link.
Glass Joe ()- Although he is not an evil villain, he is the most iconic rival for Little Mac. Not much has to be said besides how he would be a great joke character and rival.
Octolings ()- I don't know much about them personally, but i feel they would be fine editions to the smash cast as echo's.
Black Shadow()- I honestly have nothing to say about him.
Now for the spoiler/questionable spoiler section comes in:
Giygas()- Giygas is the main villain in both Mother 1 and 2. He is part of an alien race that came down to earth. He ate the fruit of knowledge and blah blah blah. It's actually a VERY interesting backstory but we aren't here to discuss the whole thing. Mewtwo looks a little heavier in this game, so having a lighter Giygas would make sense for gameplay reasons, but he would also be a great, very iconic villain from the Mother series. All of the shadow effects from Mewtwo could be replaced with red energy to reference his Mother 2 appearance, and could have music notes appear when hit.
Black Knight ()- Although i love Fire Emblem (mostly the GBA games), i'm ashamed to say i never played the Radiance games. All my informational writing on this will be from conversations with others. Black Knight aka Zelgius is the main villain of the Radiance games and is very popular within the fandom. He was trained by the same master as Ike, so having the same moves makes sense. Black Knight could be heavier due to the armour, but the armour isn't as big as some art shows, so i think it would be fine to make the model just a bit bigger than Ike's.
Masked Man ()- HONESTLY THE BIGGEST SPOILER HERE! Masked Man is Claus, Lucas's twin brother. They are also one of the most iconic villains ever to all people who have played the game, and even people haven't like me. Although they have a beam sword, gadgets, PK, and other cool things that could make an amazing and outstanding moveset, he could also work as an echo.
Hades ()- Although many would say Demise, the origin of Ganondorf, and i can honestly see why people would say this. I'm personally a Hades guy. Hades is from Kid Icarus Uprising and is the true villain of the game. He is easily the strongest character in Kid Icarus, strong enough to have to have Palutena, Viridi, the Great Blacksmith, and even a revived Medusa help Pit to beat him, and yes, all at once. His canonical strength doesn't matter though. He is an iconic Kid Icarus villain even if not the most important one. Besides the sword which could easily be replaced with something else, the moveset works PERFECTLY.
Lord Frederick ()- Donkey Kong Tropical Freeze is one of my favorite games of all time. Having the main villain of that game would be really cool. They could replace animations with ice, and make him have a few general hit animations.
Galacta Knight ()- Galacta Knight has been the secret final boss in many Kirby games now. He is very iconic and very wanted. It crushed my hopes and dreams to know he was a costume for Meta Knight. This doesn't have to stop them though. They are much more iconic than Dark Meta Knight or Morpho Knight and more popular. They could make them a major antagonist in the story too, even above villains like Bowser. They could change their final smash to an arrow barrage followed by a beam of light in a cut-scene.
Grima (:ultrobin)- Grima is the final boss of Fire Emblem Awakening with greatly expanded lore in Shadows of Valentia. They are Robin from the future after they turn into the dark dragon. With the same look as Robin, all they would need to do is add a dark effect to their model. If they wanted to go full on changes they could make the sword be a beam of dark energy and make it more consistent than the Levin/Bronze, sort of like Lucina to Marth. Also they have to replace Thoron with Dark Breathe.
Malos ()- I don't know much about Malos because i have only played Xenoblade 1 and i am only like half way through because i'm in Mechonis. I know that Malos has a similar skillset though.
Metal Sonic ()- Although Shadow seems more likely, he's not really a villain because he is redeemed. Metal Sonic unlike Shadow could be exactly the same but with different voice clips.
Spoiler Free:
Medusa ()- Medusa is the main villain of Kid Icarus and the villain in Kid Icarus Uprising (can't speak for the gameboy game because like most people i haven't played it). She is an iconic character, a character who would give Kid Icarus an easy rep, and is well liked by the community. Sure she could be unique, but loking at her backstory and even the way she fights shows that she would be perfect over Palutena.
Dark Meta Knight ()- Dark Meta Knight is the main villain in Amazing Mirror and playable in Star Allies. Although maybe not the most iconic option, they would only need a quick model swap and would give the Kirby series an easy villain, something that is difficult due to how most get redeemed. But despite how they are a dream friend, they are still portrayed as a villain.
Dark Link ()- Dark Link is simple. Just a dark Link. What they could do is they could give him the properties of Toon Link's bow and bomb to make him feel more like the old Link.
Glass Joe ()- Although he is not an evil villain, he is the most iconic rival for Little Mac. Not much has to be said besides how he would be a great joke character and rival.
Octolings ()- I don't know much about them personally, but i feel they would be fine editions to the smash cast as echo's.
Black Shadow()- I honestly have nothing to say about him.
Now for the spoiler/questionable spoiler section comes in:
Giygas()- Giygas is the main villain in both Mother 1 and 2. He is part of an alien race that came down to earth. He ate the fruit of knowledge and blah blah blah. It's actually a VERY interesting backstory but we aren't here to discuss the whole thing. Mewtwo looks a little heavier in this game, so having a lighter Giygas would make sense for gameplay reasons, but he would also be a great, very iconic villain from the Mother series. All of the shadow effects from Mewtwo could be replaced with red energy to reference his Mother 2 appearance, and could have music notes appear when hit.
Black Knight ()- Although i love Fire Emblem (mostly the GBA games), i'm ashamed to say i never played the Radiance games. All my informational writing on this will be from conversations with others. Black Knight aka Zelgius is the main villain of the Radiance games and is very popular within the fandom. He was trained by the same master as Ike, so having the same moves makes sense. Black Knight could be heavier due to the armour, but the armour isn't as big as some art shows, so i think it would be fine to make the model just a bit bigger than Ike's.
Masked Man ()- HONESTLY THE BIGGEST SPOILER HERE! Masked Man is Claus, Lucas's twin brother. They are also one of the most iconic villains ever to all people who have played the game, and even people haven't like me. Although they have a beam sword, gadgets, PK, and other cool things that could make an amazing and outstanding moveset, he could also work as an echo.
Hades ()- Although many would say Demise, the origin of Ganondorf, and i can honestly see why people would say this. I'm personally a Hades guy. Hades is from Kid Icarus Uprising and is the true villain of the game. He is easily the strongest character in Kid Icarus, strong enough to have to have Palutena, Viridi, the Great Blacksmith, and even a revived Medusa help Pit to beat him, and yes, all at once. His canonical strength doesn't matter though. He is an iconic Kid Icarus villain even if not the most important one. Besides the sword which could easily be replaced with something else, the moveset works PERFECTLY.
Lord Frederick ()- Donkey Kong Tropical Freeze is one of my favorite games of all time. Having the main villain of that game would be really cool. They could replace animations with ice, and make him have a few general hit animations.
Galacta Knight ()- Galacta Knight has been the secret final boss in many Kirby games now. He is very iconic and very wanted. It crushed my hopes and dreams to know he was a costume for Meta Knight. This doesn't have to stop them though. They are much more iconic than Dark Meta Knight or Morpho Knight and more popular. They could make them a major antagonist in the story too, even above villains like Bowser. They could change their final smash to an arrow barrage followed by a beam of light in a cut-scene.
Grima (:ultrobin)- Grima is the final boss of Fire Emblem Awakening with greatly expanded lore in Shadows of Valentia. They are Robin from the future after they turn into the dark dragon. With the same look as Robin, all they would need to do is add a dark effect to their model. If they wanted to go full on changes they could make the sword be a beam of dark energy and make it more consistent than the Levin/Bronze, sort of like Lucina to Marth. Also they have to replace Thoron with Dark Breathe.
Malos ()- I don't know much about Malos because i have only played Xenoblade 1 and i am only like half way through because i'm in Mechonis. I know that Malos has a similar skillset though.
Metal Sonic ()- Although Shadow seems more likely, he's not really a villain because he is redeemed. Metal Sonic unlike Shadow could be exactly the same but with different voice clips.