@marston:
Match 1) Harry Potter has been shown to be both willing and able to use the Unforgivable Curses in dire circumstances, so if we're talking a
Death Battle type of scenario, Harry wins. Otherwise, probably Twilight, since she'd likely be a match for Harry, power-wise, but likely has a much larger repertoire of spells at her disposal, due to how studious she is and how studious Harry isn't.
Match 2) Don't know about SATAM Sonic's specific abilities, but if he's not allowed access to his Super Sonic form, I'd give it to RD, since being able to fly is a pretty big tactical advantage. Otherwise, Sonic wins.
Match 3) Rouge may be able to fly, but Rarity can use magic, so even basic telekinesis can probably keep Rouge grounded. However, I'd probably have to give the win to Rouge, since she actually fights regularly, whereas Rarity would probably rather
whine complain her way out of a sticky situation.