Akuma

In order to learn Shun Goku Satsu, Akuma embraced the principle of Satsui no Hadō or (The Surge of the Intent to Murder/Murderous Intent). Through Satsui no Hadō, Akuma was forced to give up any compassion he held towards other human beings. In addition, Akuma realized his limits as a martial artist could be expanded, and left Goutetsu's guidance to train alone. He eventually returned and killed his master with the Shum Goku Satsu technique, as well as his brother Gouken. Sensing the hidden potential in Ryu's power, Akuma seeks out the wandering fighter to encourage him to unleash his Satsui no Hado out of his desire to fight Ryu in a fight to the death.

Akuma will only fight against opponents that he knows will give him a decent challenge in battle. If Akuma senses any weakness in a fighter or if their skills aren't to his caliber, he will deny their challenge and leave the battle. He intentionally holds back his power to give his opponents a fighting chance. Outside of battles, Akuma can be found training to keep his techniques polished for battle.
 
In the "Street Fighter Alpha" movie, there are certain hints to that Akuma might be Ryu's father.