Let's See the competitors here: we have a robot, a man who can punch a hole in the universe, and a young hero with a legendary sword.
A thousand year old princess, able to transform into the embodiment of a nightmare, wielding a sword likely with magical properties. The One who is watching over everyone while they are sleeping, able to enter dreams.
With all that in mind, it will be Luna.
Here's the Scenario: the clash slices R.O.B., directs Falcon's punch into link. Link is killed in the blast, Falcon is dazed for a split second at the loss, and the Princess finishes him off with a swift lunge into his chest.
Feel Free to agree or Disagree, but that's how it went in my head.
I'm going to go with the robot, falcon, and fairy boy on this one. She can block attacks from all 3 of them simultaneously. If going 1v1 then: Luna>R.O.B Luna?Captain Falcon Luna<Link This is coming from a guy who occasionally watches MLP and SSBB. This is my best non-bias opinion.