User blog comment:Shrek-it Ralph/Akuma VS Shang Tsung REMATCH/@comment-27009616-20151008164133/@comment-5035900-20151014034222

Just putting this out there:

Shin is canon, as it is Akuma no longer holding back on his foe and unleashing his full power.

Oni is non-canon, a What-If? Akuma who essentially loses himself to the Satsui no Hado.