Story.
Gouki, or Akuma, was the brother of Ryu and Ken's master Gouken, and was trained in the full lethal ways of Ansatsuken by his sensei Goutetsu, even learning the most dangerous technique of all- the Shun Goku Satsu. The move shocked Gouken into training his own students a non-lethal form of the art, while Gouki managed to learn the Shun Goku Satsu for himself. Killing Goutetsu in battle with this move, he goes on to challenge his brother Gouken to a battle where, ultimately, he won and killed Gouken. Victorious, he leaves the site and goes back to his island of Gokuentou (Street Fighter 1.)
On meeting up with Ryu, a student of Gouken, he challenges Ryu to a battle. Impressed by the young man's skill, he reveals to Ryu that he wields the same power as he does, the Killing Intent (Satsui No Hado). Telling Ryu that he should awaken that power and once he does, should challenge him again so they can have a real match of skill. Leaving his island, he found himself challenged by an old man called Gen-an assassin trained in Chinese elements of Ansatsuken. Performing the Shun Gok Satsu on him, but found out that the old man proved himself immune to it. Gen struck him with his Zan-ei, but Gouki survived that in turn. As the fight continued, Gouki realised Gen was sick and left- leaving the battle at a draw (Street Fighter Alpha 2.)
Searching for a worthy challenger, he found himself fighting Gen again. Proving himself more persistant than before, wanting to fight Gouki to the death and telling him that this battle won't end in another draw. Yet the battle ended again without a solid winner, but considering himself the winner- Gen spares Gouki and leaves, giving up his fighting style (Street Fighter Alpha 3.)
Hearing about the 2nd Street Fighter tournament, Gouki watches from the background before leaping into the fray against Bison in the final match to test how powerful the man really was. When he approached Bison, he caught him off-guard. Gouki declares that Bison is pathetic for 'being consumed by his own shadow' (using Psycho Power)  whereas Gouki gained his power through his fists and training. Saying that a master of the fist will always beat those who are swallowed by their shadow, he performs the Shun Goku Satsu upon Bison and kills him (Super Street Fighter 2: Turbo.)
From then on, Gouki continues to train and make himself more powerful- destroying Ayer's Rock with the Kongou-Korutsu Zan in Street Fighter 3: Double Impact, as well as destroying a submarine and a boat with a as-of-yet non-playable move Tenshoukairekijin in Street Fighter 3: 3rd Strike.

Moves.
Gou Hadouken- QCF+Any Punch Button.
Mid-Air Gou Hadouken- QCF+Any Punch Button (in mid air).
Gou Shoryuken- DPM+Any Punch Button.
Tatsumaki Zankuu Kyaku- QCB+Any Kick Button.
Ashura Senku- DPM+All Punch Buttons or All Kick Buttons.
Ashura Senku 2- RDPM+All Punch Buttons or All Kick Buttons.
Tenma Kujin Kyaku- QCF+Any Kick Button (in mid air).
Hyakki Shu- DPM+Any Kick Button.

• Hyakki Gouzan- Don't press any button.
• Hyakki Goushou- Heavy Punch.
• Hyakki Gousen- Heavy Kick.
• Hyakki Gousai- Light Punch+Light Kick at opponent's head (Street Fighter 3). Forward+Heavy Punch at opponent's head (Capcom Vs SNK).
• Hyakki Gotsui- Forward+Light Punch+Light Kick at opponent's head (Street Fighter 3). Forward+Heavy Kick at opponent's body (Capcom Vs SNK).

Super Combo's.
Messatsu Gou Hadou- HCF,HCF+Any Punch Button.
Messatsu Gou Hadou- QCB+Two Punch Buttons (in the Marvel & Street Fighter crossovers).
Messatsu Gou Shoryu- QCF,QCF+Any Punch Button.
Messatsu Gou Shoryu- QCF+Two Punch Buttons (in the Marvel & Street Fighter crossovers).
Messatsu Gou Rasen- QCF,QCF+Any Kick Button (in Street Fighter 3).
Kongu Korutsu Zan- Down,Down,Down+All Punch Buttons (in Street Fighter 3).
Tenma Gou Zanku- QCF,QCF+Any Punch Button (in mid air).
Tenma Gou Zanku- QCF+Two Punch Buttons (in the Marvel & Street Fighter crossovers).
Shun Goku Satsu- Light Punch, Light Punch, Forward,Light Kick,Heavy Punch. (level 3 super move).