Not even including Tyrion, that's just not fair. Korrin's a lot more aggressive than Bethany, so she'd probably win that if she could make it fast enough where Bethany doesn't have time to heal.
merrill and james would. ... man. i don't think she'd want to use blood magic on him. so. he'd win and tell himself it was his duty to do it probably and everything would be very sad.
Bethany and Korrin would be a solid match - you're right, Korrin would have to keep hitting Bethany so she couldn't heal. Bethany would have to keep Korrin at a distance so she can't use her Enchanter's Blade.
just don't ask how he probably got it