Ansatsuken: 暗殺拳 Murderous/Assassin's Fist
This deadly fighting style is used by many, but mastered by few. As one can deduce from the name, its primary use is for assassination, as nearly every move, special or otherwise, is designed to be a crippling or killing blow to the target.
The style is based not off of a certain style per se, but a loose concept, the origin of which is unknown. Some link it to Japan's Feudal Eras, others trace it to other countries. The elderly Chinese fighter known as Gen practices this concept with two interchangeable styles of Kung Fu, the Mourning Mantis and Hateful Crane. This analysis, however, will focus on the version created by Goutetsu.
Goutetsu: The founder of Ansatsuken Karate. He combined moves from Karate, Judo and Kenpo, and, with the application of ki, made his own style. The end result was a style that is, as a whole, lethal. He was aware of how violent his art was, but apparently did not think much on it. He knew about the Satsui no Hado and its dangers, even as he taught his students, Gouken and Akuma. If he had been more wary, it's likely that Akuma would not have been able to kill him.
These are its current living practitioners, by order of strength. While only one's fighting mannerisms are deadly enough to be considered murderous, all of these warriors practice a similar style and will be loosely referred to as practitioners of Ansatsuken for the sake of this analysis.
Dan Hibiki: This showoff was kicked out of Gouken's dojo for wanting to use the style for revenge. Nowadays, he uses a variation of the style's basics mixed with his father's, and calls it Saikyo-ryu. This, along with the relentless taunting, makes Dan the weakest Ansatsuken warrior (if you can call him that) out there. However, he doesn't lose EVERY fight. In fact, he has the potential to beat most fighters out there, given the right circumstances. It's just a shame that he's blinded by his own ego and self-satisfaction to go any further.
Sean Matsuda: He's still a novice, but takes fighting more seriously than Dan does, and, therefore, is stronger than him. Sean adds his own flair to the style and has considerable power, but still has a long way to go before he can play with the big boys.
Sakura Kasugano: The first female to use Ansatsuken is a force to be reckoned with. The high school girl has a lot of power and USES it. Her moves are somewhat unpolished since they are self-taught, but they certainly get the job done. She is currently trying her best to juggle training and schoolwork, though her number one desire is to learn from her idol/crush, Ryu. It will be interesting to see how far she is able to take her training. Do not underestimate her, at any rate.
Ken Masters: His last name should be your first clue. Ken is a very powerful fighter with an ego to match. In fact, his student, Sean, reminds Ken of himself when he was younger. Masters focuses mainly on the Shōryū (Rising Dragon) principle of Ansatsuken, and has taken it a long way. He's not the strongest, but he is certainly one of the best. Just ask him.
Ryu: The strongest of Gouken's Ansatsuken school, Ryu has dedicated his life to mastering and perfecting this style, walking the path of the true warrior. He focuses on the Hadō (Surge) principle. If you think he's perfect, you might be on to something, but tell Ryu that, and he'll deny it flatout. No matter how many fighters he's beaten (TONS), he's always looking for the one fight that will bring his search to an end. Whether or not he'll find it remains to be seen.
It's a proven fact that Ryu, like all who practice this style, possesses the ability to awaken the Satsui no Hadō power that enslaved Akuma. Keeping this Pandora's Box closed is an eternal struggle for the lonely warrior, sealed or not. Should he succumb to the urge, he will become a crazed warrior, destroying anything and anyone in his way. One can only hope that he will be able to attain the power of nothingness and bring this torture to an end.
Akuma (Gouki): One of the strongest Ansatsuken warriors ever to walk the earth...and, unfortunately, the most dangerous. He is not interested in fighting/killing at random, however, and will not bother going all out if his opponent cannot (IF he chooses to fight someone weaker at all). When Gen's leukemia disease was brought into the light, for example, Akuma left him be with honor. Anyone who challenges him and proves themselves worthy of his best, however, will run the risk of facing a cold, merciless death. Akuma doesn't let anything get in the way of victory. Not mercy, not morality...or even family. That was made clear the day he nearly killed Gouken, his own brother, in a rematch duel. Akuma, however, believed he hadn't committed murder. As far as he's concerned, it was just another battle, the strong besting the weak in a fight to the death. That's what the Satsui no Hadō does to you when fully embraced.
Gouken: Older brother of Akuma and master of Ryu and Ken. Gouken's personal fighting methods are more based on self-defense rather than outright aggressive tactics. He didn't believe that Ansatsuken should be used for killing, so he didn't incorporate the lethal moves (such as the Shun Goku Satsu) into his school. For years it had been assumed that he met his end at the blood-soaked hands of Akuma, but it appears that he has managed to attain the power of nothingness, taking his power to a level high enough to survive even the Shun Goku Satsu (though the ordeal did leave him in a coma, hence the long absence from the world of the living). Once he awoke, he wandered, testing all the new fighters that have emerged, imparting guidance to each. After this, he tested his beloved pupils and sealed the Satsui no Hado within Ryu. Shortly after that, he found himself facing down Akuma for Round 3. While the outcome is unknown, both brothers seem to have survived.
After all this time, though, he seems to be just as jovially stern with Ryu and Ken as he was during training, though he insists that he no longer has the need to guide them. At any rate, it is good to see him alive and well.
Kuruoshiki Oni: Make no mistake, this creature is no longer Akuma. This is the result of the cursed warrior allowing the Satsui no Hadō to overwhelm him. Whatever he is, he is not human, nor is he bound by the loose sense of honor Akuma once had. He exists only to destroy all life, no matter how small and insignificant. Those who face Oni may be digging an early grave...
As you can see, Ansatsuken is not a style to be taken lightly. Those who practice it are in as much danger as those who fight against it. One thing is for sure, though: it kicks much butt.
Additional analysis will be submitted at a later date.
(If you must debate me on this and other analyses, please contact me elsewhere. Thank you.)