Samus v.s. Akuma
Pretty sure it hasn't happened yet.
Base Akuma, non of that lacks-specific-feats-power-up-ness.
Takes place in a karate dojo, which will probably explode pretty quickly. They start several meters apart, however. Samus has her full gravity/fusion suit load out, and a full-up-graded beam and missile set, power bombs are in, as is space jump and sounds-like-it'd-hurt-less-than-it-does Screw attack.
Besides not being able to go Shin or Oni Akuma has no other limitations.