SSB4 with characters: [u'Falco', u'Pikachu']
Falco struggles hard against Pika for a number of reasons. One, Pika is much faster than Falco. Two, while Falco can combo Pika fairly well, Pika's combos are generally scarier. Three, Pika's short height and difficult to intercept recovery make him surprisingly hard for Falco to finish off because a short-hop back-air will whiff on a grounded Pika, and he can hardly gimp Pika. Meanwhile Pika can gimp Falco pretty effectively. At least Falco has ...

SSB4 with characters: [u'Falco', u'Yoshi']
I'd say this MU is in Yoshi's favor. Falco doesn't combo Yoshi very well because of his floatiness and neutral-air. Down tilt is still good for combos, but Falco's throws aren't when against Yoshi. Yoshi's double-jump armor makes him very difficult for Falco to edgeguard. Yoshi simply has more mobility and speed than Falco as well. However I imagine it isn't too bad for Falco because he can deflect eggs to weaken Yoshi's approaches, and ...