SSBB with characters: [u'Bowser', u'Samus']
While Bowser and Samus are two of the worst characters in Brawl, the advantage in their matchup is surprisingly clear. Samus has the advantage in neutral. Because of Bowser's very slow movement, it's a cake walk for Samus to outzone him with Grapple Beam and Missiles. Bowser, thus, has a stupidly rough approach. But that's not all: because of Bowser's size and frame data disadvantage (thus eliminating his potential advantage in close range boxing), a ...

SSB4 with characters: [u'Corrin', u'Diddy Kong']
Could someone explain why this matchup is even (let alone in Corrin's favor)?

SSB4 with characters: [u'King Dedede', u'Ryu']
Because of King Dedede's combo weakness and telegraphed moves I would actually call this one of Ryu's best matchups.