Knuckles has guarded the Master Emerald for a long time, but when it breaks (Which is often) Rouge tries to steal part of the Master Emerald. Because of this they have clashed in the past. Knuckles beat her then and he could beat her now. Knuckles is the stronger fighter and could beat her mildly easily. Rouge has hand to hand skills, but Knuckles super strength wins out on this day. Knuckles wins.