Sylux is a no-go because there is no way he would be picked over Dark Samus or Ridley (or Rundas) and it's unlikely Metroid is getting four reps.Technically since you battle against other Pokemon, all the Pokemon characters could technically be considered anti heroes, depending on whether they're on your team, or the team of the trainer you're battling. Only reason why Mewtwo is seen as a villain is because of the movies, where he starred as an evil p\Pokemon who hated humans, and wanted to replace every Pokemon with a clone, just like him. Meowth/Weezing/Arbok also fall into the same category as they are villains of the anime. So either way all four of those characters are villians of Pokemon.
Sylux and Bowser Jr. are no-goes? Says who?
Bowser jr.'s chances are way higher than the list I included him in, but Mario getting 6 reps?