I hate Harry Potter so i'll have to go with Discord Battle of The Hedgehogs Russell Ferguson vs Sonic by the way this isn't a race this is a fight.
I don't know unless Shadow went Super then i'd say the battle could go either way. Even though I don't like or have any interest in Doctor Who who would win in a fight between Dr Who and Dr Whooves?
They would spend so much time talking to each other that they would forget to fight. Prius vs Freight Train.
Mecha Godzilla: one stomp and Metal Sonic is pancake Nicola Tesla or Thomas Edison, both armed with weapons based off their inventions