The Satsui no Hado can only be tapped into if the user is willing to commit murder to fight a battle.
Akuma is good enough at this style of martial arts that he was able to defeat Gouken, another master martial artist. The martial art contains aspects of Karate, Kenpo, and Judo.
Akuma, originally named Gouki, and his brother Gouken were students of a martial arts master named Goutetsu.