Oni

"I shall grind beneath my heel...all that exists."

- Super Street Fighter 4 Arcade Edition

Oni is a secret character in the Street Fighter series. He can be fought as a secret boss in Arcade Mode, as well as being a playable character. Oni is in fact, Akuma who has let Satsui no Hado consume him to the point where he has discarded humanity, and has taken the form of a demon.

Note: This character should not be mistaken as Shin Akuma, even though both have very close similarities to each other such as being a more powerful form of Akuma.

Appearance
Oni appears as a far more muscular and slightly larger version of Akuma. He has dark blue skin, glowing yellow-red eyes and glowing, spiky shoulder length hair. He also gains fangs and short protrusions on his forehead, resembling growing horns. The top half of his gi has been been blown off, showing off his stature and the prayer beads that were once around his neck now float about disconnected around his body.

Super Street Fighter IV
Main article: Super Street Fighter IV

Oni possesses an air dash attack, the direction of which is determined by the punch button pressed. He also possesses a dashing slash which allows him to pass the opponent by, similar to his Ashura Senku. He also possesses a jumping smash attack which has been compared to E. Honda's Sumo Smash. It also appears that he no longer possesses his Hyakkishu attack. His heavy punch now has the ability to nullify projectiles as well.

His Super Combo, the Raging Demon, remains intact, but now can be used in mid-air. His Ultra Combos are new and appear to be based on Super Arts from Street Fighter III: 3rd Strike.

His first Ultra Combo, Meido Gohado, is an advanced Messatsu Gou Hadou that can be fired from the air. Oni needs to be close and on the ground in order to force his opponent right into the wall in order to blast them with another, with the force of the projectile emitting energy from behind the opponent shaping into Oni's kanji character.

His second Ultra Combo, Tenchi Sokaigen, appears to be a precursor to his Kongou Kokuretsu Zan attack, where he only forms an eruption of energy in front of him. Like the Meido Gohado, Oni needs to be close enough to launch his opponent up into the air in order to slam them with a left-handed Shoryuken to the opponent's exposed back.

Trivia

 * In Japanese mythology, an Oni is a type of Ogre or Demon. This serves as a connection to both the names Gouki (Essentailly Strong Oni / Strong Demon) and Akuma (Devil). He may also be an official version of the fan based version of Akuma called Ogre Akuma, most notable as a character in MUGEN. However, Akuma states throughout the series that he is a demon, and Oni may be the subject of these particular statements, thus classifying Oni as a demon.
 * The character page also states that Oni is Akuma transformed into a literal demon instead of a metaphorical one. How he got this way is still unknown, but the most plausible explanation is that Oni is the result of Akuma and the Satsui no Hadou becoming one and the same.
 * Whenever Oni wins the fight, he physically interacts with the opponent's character. He picks them up by their heads, then (offscreen) supposedly deals a killing blow. This is the only character in the game that shows physical contact with the opponent after winning a match.
 * Oni seems to have hair that is similar to that of a Super Saiyan state and whenever his prayer beads float around him, they look like Dragon balls from the Dragonball Z (Dragonball Z Kai) series.
 * Oni's theme in Super Street Fighter IV is an alternate remix of Akuma's theme from Street Fighter II.
 * In Super Street Fighter IV, there is a Shin version of Oni. When he fires a Hadouken, it would be fully charged and could travel through the whole screen. He would also move faster and the way he walks is different, he floats as he moves around.
 * Oni's fighting stance resembles the artwork of Shin Akuma from SNK Vs Capcom: Chaos.
 * In Akuma's ending of Street Fighter Alpha 2, he has enough power to destroy an entire island. In Shin Akuma's ending of Capcom Fighting Evolution, he has tested his power on a comet and had completely destroyed it, this ending shows that Shin Akuma has enough power to destroy a comet third-size of Earth, In Oni's ending in Super Street Fighter IV, Oni has the power to cause a volcano to erupt by dealing a single blow to the volcano, but this is most likely a small piece of his power, because in the beginning of Super Street Fighter IV Arcade Edition, he is so powerful that he was able to destroy a large tree with just his aura alone.
 * Oni's Ultra Combos are the only ones (aside from both of Akuma's Ultras) show a black and white changing background.
 * Also, if either Ultra Combo is a finishing move, no "KO" sign will be shown on the screen. The opponent is not seen to physically fall over, but shown collapsed in the ground or midair, implying that Oni has actually killed the opponent.
 * Right after Oni hits the volcano in his ending of Super Street Fighter IV Arcade Edition, he was seen floating in the air. He is also seen floating in one of his win poses where he states "I am not human". It is possible that whenever Akuma is in this form, he gains the ability to defy gravity.