Hi, long time no see, but I've got a new suggestions:
Katsuki Bakugou (My Hero Academia) vs Blast Man (Mega Man) - two dangerous, volatile, and a bit short-tempered with explosive abilities. Former friend of Izuku Midoriya vs reprogrammed younger brother of Mega Man
Segata Sanshiro (SEGA) vs Ichiro Ogami (Sakura Wars) - it's a fight between two SEGA characters and romantic interests of Sakura Shinguji
Kotomine Kirei (Fate/Stay) vs Enrico Pucci (JoJo's Bizarre Adventure) - "The worst kind of evil is the one who thinks that he's good" Two antagonistic fatalistic priests and both even befriended with egoistic blond half-humans and even share a voice actor.
Princess Zelda (The Legand of Zelda) vs Metroids (Metroid) - a joke battle. Sorry hero, but this game is named after me.
Shaggy Rogers (Scooby-Doo) vs Jeff the Killer - anotherr joke battle. Hero vs Villain, two skinny teens with super strength, one is a monster who hunts people while the other hunts people who dressed as monsters.